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A* r 



AN INTEODUCTION TO THE STUDY 



COMPOUNDS OF CARBON 
ORGANIC CHEMISTRY 



BY 
IRA REMSEN 

PRESIDENT OF THE JOHNS HOPKINS UNIVERSITY 



FOURTH REVISION 



BOSTON, U.S.A. 

D. C. HEATH & CO., PUBLISHERS 

1903 



THE LIBRARY OF 
CONGRESS, 

Two Copies Received 

MAY 18 1903 

Copyright Entry 

h U^v j 8'- / <T 3 ! 

CLASS Off,- XXc. No, 

^ q q <f 



COPY 



Copyright, 1885, 1901, and 1903, 
By IRA REMSEN. 



PREFACE TO FIRST EDITION. 



This book is intended for those who are beginning the subject. 
For this reason, special care has been taken to select for treatment 
such compounds as best serve to make clear the fundamental prin- 
ciples. General relations as illustrated by special cases are discussed 
rather more fully than is customary in books of the same size ; and, 
on the other hand, the number of compounds taken up is smaller 
than usual. The author has endeavored to avoid dogmatism, and 
to lead the student, through a careful study of the facts, to see for 
himself the reasons for adopting the prevalent views in regard to the 
structure of the compounds of carbon. Whenever a new formula is 
presented, the reasons for using it are given so that it may afterward 
be used intelligently. It is believed that the book is adapted to the 
needs of all students of chemistry, whether they intend to follow 
the pure science, or to deal with it in its applications to the arts, 
medicine, etc. It is difficult to see how, without some such general 
introductory study, the technical chemist and the student of medicine 
can comprehend what is usually put before them under the heads 
of "Applied Organic Chemistry" and " Medical Chemistry." 

Without some direct contact with the compounds considered, it 
is impossible to get a clear idea regarding them and their changes. 
A course of properly selected experiments, illustrating the methods 
used in preparing the principal classes of compounds, and the funda- 
mental reactions involved in their transformations, wonderfully Facili- 
tates the study. The attempt has been made to give directions for 
such a course. More than eighty experiments which could be per- 
formed in any chemical laboratory are described; and it is hoped 
that the plan may meet with approval. The time required to 
perform a fair proportion of these experiments is not great : and 
the results in the direction of enlarging the student's knowledge 
of chemical phenomena, will, it is firmly belieNed. furnish ;i full 
Compensation for the lime spent. 

iii 



IV PREFACE. 

The order in which the topics are taken np will be found to differ 
somewhat from that commonly adopted. The object in view was, 
however, not to find a new method, but to find one which would 
bring out as clearly as possible the beauty and simplicity of the 
relations which exist between the different classes of carbon com- 
pounds. The reasons for the method used are given in the body 
of the book. 



PREFACE TO FOURTH REVISION. 

The important advances that have been made in the field of 
organic chemistry during the past few years have made a thorough 
revision of this book necessary. The present edition gives the results 
of the revision. The principal changes and additions will be found 
in the chapters dealing with the Sugars, Stereoisomerism, the Diazo 
Compounds, and the Terpen es. The treatment of the Aromatic 
Compounds is, in general, fuller than in the older editions. Although 
considerable has been added, the size of the volume has not been 
markedly increased, the difference between the last edition and the 
present being only about fifty pages. In addition to the changes 
indicated above, minor changes have been made throughout, and 
the author believes that the book is now fully in harmony with the 
present state of organic chemistry. 

January, 1903. 



CONTENTS. 

CHAPTER I. 
Introduction. 

PAGE 

Sources of compounds. — Purification of the compounds. — Deter- 
mination of the boiling-point. — Determination of the melting- 
point. — Analysis. — Formula. — Structural formula. — General 
principles of classification of the compounds of carbon . . 1 

CHAPTER II. 

Methane and Ethane. — Homologous Series. 

Methane. — Ethane 20 

CHAPTER III. 

Halogen Derivatives of Methane and Ethane. 

Substitution. — Chloroform. — Iodoform. — Di-chlor- ethanes. — 

Isomerism 20 

CHAPTER IV. 

Oxygen Derivatives of Methane and Ethane. 

Alcohols. — Methyl alcohol. — Ethyl alcohol. — Fermentation. — 
Ethers. — Ethyl ether. — Mixed ethers. — Aldehydes. — Formic 
aldehyde. — Acetic aldehyde. — Paraldehyde. — Rfetaldehyde. 
— Chloral. — Acids. — Formic acid. — Acetic acid. — Acetic 
anhydride. — Acetyl chloride. — Ethereal salts. — Ketones. — 
Acetone ; * 

CHAPTER V. 

Sulphur Derivatives of Methane and Ethane 
Mercaptans. — Sulphur others. — Sulphonio aoids . . . .71 



VI CONTENTS. 

CHAPTER VI. 
Nitrogen Derivatives of Methane and Ethane. 

PAGE 

Cyanogen. — Hydrocyanic acid. — Cyanides. — Cyanuric acid. — 
Sulpho-cyanic acid. — Cyanides. — Isocyanides or carbamines. 

— Cyanates and isocyanates. — Sulpho-cyanates. — Isosulpho- 
cyanates or mustard oils. — Substituted ammonias or amines. 

— Hydrazine compounds. — Nitro-compounds. — Mtroso- and 
isonitroso-compounds. — Fulminic acid 79 

CHAPTER VII. 

Derivatives of Methane and Ethane containing- 
Phosphorus, Arsenic, etc. 

Phosphorus compounds. — Arsenic compounds. — Zinc ethyl. — 

Sodium ethyl. — Retrospect 103 

CHAPTER VIII. 

The Hydrocarbons of the Marsh-Gas Series, or Paraffins. 

Petroleum. — Synthesis of paraffins. — Isomerism among the paraf- 
fins. — Hexanes 108 

CHAPTER IX. 

Oxygen Derivatives of the Higher Members of the 
Paraffin Series. 

Alcohols. — Normal propyl alcohol. — Secondary propyl alcohol. — 
Secondary alcohols. —Butyl alcohols. — Pentyl or amyl alco- 
hols. — Aldehydes. —Acids. — Patty acids. — Propionic acid. 

— Butyric acids. — Valeric acids. — Palmitic acid. — Stearic 
acid. — Soaps. — Polyacid alcohols and polybasic acids. — Di- 
acid alcohols. — Ethylene alcohol or glycol. — Dibasic acids. — 
Oxalic acid. — Malonic acid. — Succinic acids. — Pyrotartaric 
acid. — Tri-acid alcohols. — Glycerol. — Ethereal salts of gly- 
cerol. — Fats. — Tri-basic acids. — Tetr-acid alcohols. — Pent- 
acid alcohols. — Hex-acid alcohols. — Hept-acid alcohols, etc. . 120 



CONTENTS. Vll 

CHAPTER X. 

Mixed Compounds. — Derivatives of the Paraffins. 

PAGE 

Hydroxy -acids, C n H 2n 03. — Carbonic acid. — Glycolic acid. — Lactic 
acids. — Hydracrylic acid. — Physical isomerism. — Hydroxy- 
sulphonic acids. — Isethionic acid. — Lactones. — Hy droxy-acids, 
C n H 2n 04. — Glyceric acid. — Other Hydroxy-monobasic acids. 
Mannonic acids. — Gluconic acids, etc. — Hydroxy -acids, 
C n H 2n -205. — Tartronic acid. — Malic acids. — Hydroxy- acids, 
C n H 2n -206. — Mesoxalic acid. — Tartaric acid. — Racemic acid. 

— Inactive tartaric acid. — Hydroxy-acids, C n H 2n _ 4 07. — Citric 
acid. — Hydroxy-acids, C n H 2n _ 2 8 . — Saccharic acid. — Mucic 
acid 155 

CHAPTER XI. 
Carbohydrates. 

Monosaccharides. — Trioses and tetroses. — Glycerose. — Erythrose. 

— Pentoses. — Arabinoses. — Xylose. — Rhamnose. — Hexoses. 

— Glucose. — Fructose. — Mannose. — Galactose. — Gulose. — 
Polysaccharides or complex sugars. — Cane sugar. — Sugar of 
milk. — Maltose. — Polysaccharides not resembling sugars. — 
Cellulose. — Gun cotton. — Paper. — Starch. — Glycogen. — 
Dextrin. — Gums 182 

CHAPTER XII. 

Mixed Compounds containing- Nitrogen. 

Amino-acids. — Amino-formic acid. — Glycocoll. — Sarcosine. — 
Amino-propionic acids. — Cystine. — Leucine. — Amino-sul- 
phonic acids. — Taurine. — Amino-dibasic acids. - Aspartio 
acid. — Acid amides. — Asparagine. Succinimide. - Cyan- 
amides. — Guanidine. — Creatine. — Creatinine, i pea or car- 
bamide and derivatives. —Substituted uveas. Ureids. Para- 
banic acid. — Ozalurio acid. ■ Barbituric acid. Sulpho urea. 

— Uric acid. — Xanthine. • -Theobromine. Caffeine. Guan- 
ine. — Retrospect 202 



Vlll CONTENTS. 



CHAPTER XIII. 

Unsaturated Carbon Compounds. — Distinction between 
Saturated and Unsaturated Compounds. 

PAGE 

Ethylene and its derivatives. — Ethylene. — Alcohols, C n H 2n O. 

— Allyl alcohol. — Allyl mustard oil. — Acrolein. — Acids, 
C n H 2n -202. — Acrylic acid. — Crotonic acid. — Oleic acid. — 
Polybasic acids of the ethylene group. — Fumaric and maleic 
acids. — Acids, C5H 6 4 . — Aconitic acid. — Acetylene and its 
derivatives. — Acetylene. — Propargyl alcohol. — Acids, 
C n H 2n — 4O2. — Propiolic acid. — Tetrolic acid. — Sorbic acid. — 
Linolei'c acid. — Valylene. — Dipropargyl 223 

CHAPTER XIV. 

The Benzene Series of Hydrocarbons. — Aromatic 
Compounds. 

Benzene. — Toluene. — Xylenes. — Ethyl-benzene. — Mesitylene. — 
Pseudocumene. — Cymene. — Hexahydrobenzenes, naphthenes. 

— Hexamethylene. — Tetrahydrobenzenes. — Tetrahydrotolu- 
ene. — Hydrocarbons, CioH 18 . — Hydrocamphene. — Menthene. 

— Dihydrobenzenes . . . . . . . . 249 

CHAPTER XV. 

Derivatives of the Hydrocarbons, C n H2n-6, of the 
Benzene Series. 

Halogen derivatives of benzene. — Chlor-benzene. — Brom-benzene. 

— Iodo-benzene. — Phenyliodoso chloride. — Iodoxy-benzene. 

— Diphenyliodonium hydroxide. — Dibrom-benzene. — Halo- 
gen derivatives of toluene. — Halogen derivatives of the higher 
members of the benzene series. — Nitro compounds of benzene 
and toluene. — Mono-nitro-benzene. — Dinitro-benzene. — Nitro- 
toluenes. — Amino compounds of benzene, etc. — Aniline. — 
Dimethyl-aniline. — Diphenylamine. — Acetanilide. — Tolui- 
dines. — Diazo compounds of benzene. — Diazo-amino com- 
pounds. — Azo- benzene. — Hydrazo-benzene. — Hydrazines. — 
Phenylhydrazine. — Sulphonic acids of benzene. — Sulphanilic 
acid. — Helianthin. — Diphenylamine orange. — Phenols, or 



CONTENTS. ix 



hydroxyl derivatives of benzene, etc. — Mon-acid phenols. — 
Phenol. — Methyl-phenyl ether. — Tri-nitro-phenol. — Amino- 
phenols. — Phenol-sulphonic acids. — Phenyl mercaptan. — 
Cresols. — Thymol. — Di-acid phenols. — Pyrocatechol. — Guaia- 
col. — Resorcinol. — Styphnic acid. — Hydroquinol. — Orcinol. 

— Tri-acid phenols. — Pyrogallol. — Phloroglucinol. — Alcohols 
of the benzene series. — Benzyl alcohol. — Aldehydes of the 
benzene series. — Oil of bitter almonds. — Cuminic aldehyde. — 
Benzaldoximes. — Acids of the benzene series. — Monobasic 
acids, C n H 2n -802. — Benzoic acid. — Benzoyl chloride. — Sub- 
stitution products of benzoic acid. — Nitro-benzoic acids. — 
Anthranilic acid. — Isatine. — Hippuric acid. — Toluic acids. — 
a-Toluic acid. — Oxindol. — Mesitylenic acid. — Hydro-cinnamic 
acid. — Hydro-carbo-styril. — Dibasic acids, C n H 2n -io04. — 
Phthalic acid. — Isophthalic acid. — Terephthalic acid. — Hexa- 
basic acid. — Mellitic acid. — Phenol-acids, or Hydroxy-acids 
of the benzene series. — Salicylic acid. — Salol. — Oxybenzoic 
acid. — Para-oxybenzoic acid. — Anisic acid. — Di-hydroxy- 
benzoic acids, C7H 6 04. — Protocatechuic acid. — Vanillic acid. 

— Vanillin. — Piperonal. — Tri-hydroxy-benzoic acids, C 7 H 6 5 . 

— Gallic acid. — Tannic acid. — Ketones and allied derivatives 
of the benzene series. — Quinones. — Pyridine bases. — Pyridine. 

— Lutidines. — Conyrine. — Conine. — Terpenes. — Olefin-ter- 
pene group. — Geraniol. — Limonene. — Camphene group. — 
Pinene. — Camphene. — Camphors. — Borneol. — Camphor 

CHAPTER XVI. 

Di-phenyl-methane, Tri-phenyl-methane, Tetra-phenyl- 
methane, and. their Derivatives. 

Tri-phenyl-methane. — Trmitxo-triphenyl-methane. — Triamino- 
triphenyl-methane. — Tri-phenyl-methane dyes.— Aniline dyes. 

— Para-rosaniline. — Rosaniline. - Hexa-methyl para-rosani- 
line. — Phthalei'ns. — Phenol-phthalel'n. — Fluorescein. -- Eosin 

CHAPTEB XVII. 
Hydrocarbons, O n Ha n a, and Derivatives 

Styrene. — Styryl alcohol. — Cinnamic acid. - Nitro-cinnamic acids. 

— Amino-cinnamic aoids. — Coumario 



X CONTENTS. 

CHAPTER XVIII. 
Phenyl-acetylene and Derivatives. 

PAGE 

Phenyl-acetylene. — Phenyl-propiolic acid. — Ortho-nitro-phenyl- 
propiolic acid. — Indigo and allied compounds. — Indigo-blue. 

— Indigo-white 370 

CHAPTER XIX. 

Hydrocarbons containing- Two Benzene Residues in 
Direct Combination. 

Diphenyl. — Benzidine. — Carbazol. — Naphthalene. — Derivatives 
of naphthalene. — Naphthylamines. — Naphthols. — Quinoline 
and analogous compounds. — Quinoline — Quinaldine. — Lepi- 
dine. — Carbostyril. — Isoquinoline 375 

CHAPTER XX. 

Hydrocarbons containing- Two Benzene Residues in 
Indirect Combination. 

Anthracene. — Anthraquinone. — Alizarin. — Purpurin. — Phenan- 

threne . . . 396 

CHAPTER XXI. 

Glucosides. — Alkaloids, etc. 

Aesculin. — Amygdalin. — Helicin. — Myronic acid. — Salicin. — 
Saponin. — Alkaloids. — Quinine. — Cinchonine. — Cocaine. — 
Nicotine. — Morphine. — Narcotine. — Piperine. — Piperidine. 

— Strychnine 404 

Index 409 



OHEMISTET 



COMPOUNDS OF CARBON. 

CHAPTER I. 
INTRODUCTION. 

In studying the compounds of carbon, one cannot fail to 
be struck by their large number, and hy the ease with which 
they undergo change when subjected to various influences. 
Mainly on account of the large number, though partly on 
account of peculiarities in their chemical conduct, it is custom- 
ary to treat of these compounds by themselves. At first, 
General Chemistry was divided into Inorganic and Organic 
Chemistry, as it was believed that there were fundamental 
differences between the compounds included under the two 
heads. Those compounds which form the mineral portion of 
the earth were treated under the first head, while those which 
were found ready formed in the organs of plants or animals 
were the subject of organic chemistry. It was believed that, 
as the organic compounds are elaborated under the influence of 
the life process, there must be something about them which 
distinguishes them from the inorganic compounds in whoso for- 
mation the life process has no part. Gradually, however, (his 
idea has been abandoned ; for, one by one, many of the com- 
pounds which are found in plants and animals have been made 
in the chemical laboratory, and without tho aid of the Life 
process. The first instance o[ the preparation of an organic 
compound by an artificial method was that of urea. This sub- 
stance was obtained by Wohloriu L828 from ammonium cyanate. 
When a water solution of the latter is allowed bo evaporate, urea 



Z INTRODUCTION. 

is deposited. Up to the time of Wohler's discovery, the 
formation of urea, like that of other organic compounds, was 
thought to be intimately and necessarily connected with life ; 
but it was thus shown that it could be formed without the inter- 
vention of life. Afterward, it was shown that potassium 
cyanide can be made by passing nitrogen over a heated mixture 
of carbon and potassium carbonate ; and, as potassium cyanate 
can be made from the cyanide by oxidation, it follows that 
urea can be made from the elements. Finally, in 1856, Berthe- 
lot succeeded in making potassium formate by passing carbon 
monoxide o^er heated potassium hydroxide ; and in making 
acetylene, a compound, the composition of which is represented 
by the formula C 2 H 2 , by passing electric sparks between elec- 
trodes of carbon in an atmosphere of hydrogen. Since that 
time, every year has witnessed the artificial preparation, by 
purely chemical means, of compounds of carbon which are found 
in the organs of plants and animals. 

It hence appears that the formation of the compounds of 
carbon is not dependent upon the life process ; that they are 
simply chemical compounds governed by the same laws that 
govern other chemical compounds ; and the name, Organic 
Chemistry, signifying, as it does, that the compounds included 
under it are necessarily related to organisms, is misleading. 
Organic chemistry is nothing but the Chemistry of the Com- 
pounds of Carbon. It is not a science independent of inorganic 
chemistry, but is just as much a part of chemistry as the chem- 
istry of the compounds of sodium, or of the compounds of 
silicon, etc. 

The name Chemistry of the Compounds of Carbon has been 
objected to as being too broad. Strictly speaking, this title 
includes the carbonates, and it is customary to treat of these 
widely distributed substances under the head of Inorganic 
Chemistry. Most books on Inorganic Chemistry also deal with 
some of the simpler compounds of carbon, such as the oxides, 
cyanogen, marsh gas, etc. 



SOURCES OF COMPOUNDS. 6 

This objection is of weight only as far as the carbonates 
are concerned, and it does not appear strong enough to make 
the introduction of a new name necessary. It should be men- 
tioned, however, that the name Chemistry of the Hydrocarbons 
and their Derivatives has been suggested. The exact signifi- 
cance of this name will appear when the compounds with 
which we shall have to deal come up for consideration. 

Sources of compounds. — The compounds of carbon are, 
for the most part, made in the laboratory; but in preparing 
them we usually start with a few fundamental compounds 
that are formed by natural processes. A large number, such 
as the sugars, starch, cellulose, and the alkaloids, of which 
morphine, quinine, and nicotine are examples, occur ready 
formed in plants, but always mixed with other substances. 
Others, such as urea, uric acid, albumin, etc., occur in animal 
organisms. Petroleum, which has been formed in nature by 
processes, the exact nature of which has not yet been satis- 
factorily explained, contains a large number of compounds con- 
sisting of only carbon and hydrogen ; and these compounds 
serve as the starting-points in the preparation of a large number 
of derivatives. When coal is heated for the purpose of manu- 
facturing illuminating gas, a very complex mixture of liquid 
and solid products is obtained as a by-product, known as coal 
tar. This substance yields some of the most valued compounds 
of carbon. A larger number of the compounds of carbon arc 
obtained from this than from any other one source. AY lion 
bones are heated in the manufacture of bone-black, an oil 
known as bone oil is obtained. This also has proved to be 
the source of a large number of interesting compounds. In 
the preparation of charcoal In heating wood, the liquid prod- 
ucts are sometimes condensed, and they form the source of 
several important compounds, among which may be mentioned 
wood spirits or methyl alcohol, acetone, and pyrolioi icons or 
acetic acid. 



4 INTRODUCTION. 

Finally, we are dependent upon the process known as /er- 
mentation for a number of the most important compounds of 
carbon. Fermentation, as will be shown, is a general term, 
signifying any process in which a change in the composition of 
a body is effected by means of minute animal or vegetable 
organisms. The best known example of fermentation is that 
of sugar, which gives rise to the formation of ordinary alcohol. 
Alcohol in turn serves as the starting-point for the preparation 
of a large number of compounds. 

Purification of the compounds. — Before the natural 
compounds of carbon can be studied chemically, they must, of 
course, be freed from foreign substances ; and before the con- 
stituents of the complex mixtures, petroleum, coal tar, and bone 
oil can be studied, they must be separated and purified. The 
processes of separation and purification are, in many cases, 
extremely difficult. If the substance is a solid, different 
methods may be used according to the nature of the substance, 
Crystallization is more frequently made use of than any other 
process. This is well illustrated, on the large scale, in the 
refining of sugar, which consists, essentially, in dissolving the 
sugar in water, filtering through bone-black, which absorbs 
coloring matter, and then evaporating down to crystallization. 
When two or more substances are found together, they may, in 
many cases, be separated b}~ what is called fractional crystalliza* 
Hon. This consists in evaporating the solution until, on cool- 
ing, a comparatively small part of the substance is deposited. 
This deposit is filtered off, and the solution further evaporated ; 
when a second deposit is obtained, and so on to the end. The 
successive deposits thus obtained are then recrystallized, each 
separately, until, finally, the deposits are found to be homo- 
geneous. 

The chief solvents used are water, alcohol, ether, benzine, 
and bisulphide of carbon ; alcohol being the one most generally 
applicable. 



PURIFICATION OF THE COMPOUNDS. 



In the case of liquids, the process of distillation is used. 
The apparatus commonly used is illustrated in Fig. 1» 




''iiiiniiiiiiiniiiiiiiuiiiiiiniiiiii 



■■■■■■■■Ml 

Fig. 1. 



The only part of the apparatus that requires explana- 
tion is the tube A. This is known as the distilling tube. 
It is simply a straight glass 
tube, about 16 cm long and 12 to 
14 mm in diameter, to which is 
attached a smaller branch some- 
what inclined downward. The 
object of the tube is to accom- 
modate a thermometer B, which 
is so fixed by means of a cork, 
that it is in the centre of the 
larger tube, and its bulb direct ly 
opposite the opening of the 
smaller branch. 

For small quantities of liquids, 




the distilling flask is much used. 



This is a long-necked, round 



INTRODUCTION. 



t % ? T ; be fitted directiy int ° the * eck ' » — « 

m *ig 2. In this apparatus, the thermometer is fitted into 
he neck of the flask in the same relation to the exit tube an 
the larger apparatus. 

For the separation of liquids of different boiling-points the 
process of fractional or partial distillation is much used When 
a mixture of two or more liquids of different boiling-points is 

fro k / " h T tiCed ^^ the boi ^-PO-t g-dualy s 
fiom that of the lowest boiling substance to that of the hlhest 
Tims, ordinary alcohol boils at 78°, and water at 100°. If the 
two are mixed and the mixture distilled, it will be found that it 
begins to boil at 78°, but that very little passes over at th 
temperature. Gradually, as the distillation proceeds the t„ 
perature indicated by the thermometer becomes U g t * nd 
higher until at last 100° is reached, when all distils over. Now 
the distillates obtained at the different temperatures differ from 
each other m composition. Those obtained at the low tem 
peratures are richer in alcohol than those obtained at the hiSer 
temperatures but none of them contains pure alcohol oi pure 
water. In order to separate the two, therefore, we must pro 
coed as follows : A number of clean, dry flasks are prepa d for 
collecting the distillates. The boiling is begun and the ZZ 

+ ~±i . agrees {6, o, or 10, according to the char- 

acterof the mature) is collected in the first flask. Ther cetv r 
is then changed, without interruption of the boiling, and th 
which passes over while the mercury rises throng! ano her 
interval equal to the first is collected in the second Lk i e 
rece.vens agam changed, and a third distillate collected- and 
so on, until the liquid has all been distilled over. It has thus 
been separated into a number of fractions, each of whTch Ja 
passed over at different temperatures. In the case Tl^l 
and water, for example, we might have collected distillate l^ 
78 to 83 , from 83° to 88°, from 88° to 93°, from 93° to 98°, 



PURIFICATION OF THE COMPOUNDS. 7 

from 98° to 100°, Now a clean distilling flask is taken, and 
into this the first fraction is poured. This is distilled until the 
thermometer marks the upper limit of the original first fraction, 
the new distillate being collected in the flask which contained the 
first fraction. When this upper limit is reached, the boiling is 
stopped. It will be found that there is some of the liquid left 
in the distilling flask. That is to say, assuming that in the first 
distillation the first fraction was collected between 78° and 83°, 
on boiling this traction the second time it will not all come over 
between these points ; when 83° is reached some will be left in 
the flask. The second fraction is now poured into the distilling 
flask through a funnel tube, and the boiling is again started. 
Of the second fraction, a portion will pass over below the point 
at which it began to boil when first distilled. Collect in the 
proper flask, and continue the boiling until the thermometer 
marks the highest point of the fraction last introduced, changing 
the receiver whenever the indications of the thermometer require 
it. Now stop the boiling, and pour in fraction No. 3, and so 
on until all the fractions have been subjected to a second distil- 
lation. On examining the new fractions, it will be found that 
the liquid tends to accumulate in the neighborhood of certain 
points corresponding to the boiling-points of the constituents of 
the mixture. The distilling flask is now cleaned, and the whole 
process repeated. A further separation is thus effected. By 
continuing the distillation in this way, pure substances can, in 
most cases, eventually be obtained. That the fractions are 
pure can be known by the fact that the boiling-points remain 
constant. In some cases perfect separation cannot be effected 
by means of fractional distillation ; as, for example, in the 
case of alcohol and water. But still it is valuable, even in 
such cases, as it enables us to purify the substances, at least 
partially. 

The best examples of distillation carried on on the large scale 
are those of alcohol and petroleum. Probably the best example 
of fractional distillation is that oi' the li^ht oil obtained from 
coal tar. 



8 INTRODUCTION. 

Experiment 1. Mix equal parts (about half a litre of each) of alco- 
hol and water. Distil through four or five times, and notice the 
changes in the quantities obtained in the different fractions. 

Determination of the boiling-point . — In dealing with 
liquids, it often is extremely difficult to tell whether they are 
pure or not. The first and most important physical property 
which is utilized for this purpose is the boiling temperature, 
commonly called the boiling-point. This is determined by 
means of an apparatus, such as is described above as used for 
distilling. The temperature noted on the thermometer when 
the liquid is boiling is the boiling-point. When great accuracy 
is required, the point observed directly must be corrected, in 
consequence of the expansion of the glass and the cooling of 
that part of the column of mercury which is not in the vapor. 
Full directions for making these corrections can be found in 
larger books. A pure chemical compound always has a con- 
stant boiling-point. 

Determination of the melting-point. — Just as the boil- 
ing-point is a very characteristic property of liquid bodies, so 
the melting-point is an equally characteristic property of many 
solid bodies. If a substance begins to melt at a certain tem- 
perature, and does not melt completely at that temperature, it 
is, in all probability, impure. By means of the melting-point 
minute quantities of impurities, which might readily escape 
detection 03^ other means, are often found. In dealing with the 
compounds of carbon, determinations of melting-points are very 
frequently made. In general,, only those compounds which have 
-onstant melting-points are to be regarded as pure. The deter- 
mination is made as follows : Small tubes are prepared by 
heating a piece of ordinary soft glass tubing of 4 mm to 5 mm 
diameter, and drawing it out. If the parts are drawn apart 
about 12 cm to 15 cm , two small tubes may be made from the 
narrowed portion by melting together in the middle, and then 
filing off each piece where it begins to grow wider near the 



DETERMINATION OF THE MELTING-POINT. 



3 



large tube. These small tubes must have thin walls, and be 
of such internal diameter that an ordinary pin can be intro- 
duced into them. A small quantity of the substance to be 
tested is placed in one of the tubes, enough to make a minute 
column of about 5 mm in height. The tube containing the 
substance is fastened to a thermometer by means of a small 
rubber band cut from a piece of rubber tubing. The band is 
placed near the upper part of the tube, and the lower part of 
the tube, containing the substance, is placed against the bulb 
of the thermometer. Now a beaker glass of about 100 cc 
capacity ^ is filled with pure paraffin, and the latter melted. 
When it is in liquid condition, the thermometer, with the tube 
and substance, is introduced 
into it, and the heating con- 
tinued with the aid of a 
small flame until the sub- 
stance melts . The instant it 
melts the temperature indi- 
cated by the thermometer 
is noted. This is the melt- 
ing-point required. It is 
necessary, however, to cor- 
rect the observed point in 
the same way as in the case 
of the boiling-point. Some- 
times, instead of paraffin, 
concentrated sulphuric acid 
is used in the bath ; and 
instead of a beaker, a small 
round-bottomed flask. For ^ 
substances which melt below 

80°, the temperature at which ordinary paraffin is liquid, water 
or sulphuric acid should be used. 

Experiment 2. Determine the melting-points of a few substances, 

such as urea ami tartaric acid, if they do not melt at definite points. 
recrystallize them until they do. Note the melting-points observed, 




10 INTRODUCTION. 

and see how well they agree with those stated in the book. The 
arrangement of the apparatus above described is shown in Eig. 3. To 
secure a uniform temperature of the bath, it should be gently stirred 
with a glass rod during the experiment. The mercury of the ther- 
mometer should rise slowly. 

Analysis. — Having purified the compounds, the next step 
is to determine their composition. A comparatively small num- 
ber of the compounds ordinarily met with consist of carBon and 
hydrogen only ; the largest number consist of these two elements 
together with oxygen ; many contain carbon, hydrogen, oxygen, 
and nitrogen. But, in the derivatives of the fundamental com- 
pounds, all other elements may occur. Thus the hydrogen may 
be partly or wholly replaced by chlorine, bromine, or iodine, as 
in the so-called substitution-products ; and any metal may occur 
in the salts of the acids of carbon. The estimation of carbon 
and hydrogen is the principal problem in the analysis of the 
compounds of carbon. This is effected by what is known as 
the combustion process. A known weight of the substance is 
completely oxidized, the carbon being thus converted into car- 
bon dioxide, and the hydrogen into water. These two products 
are collected, the carbon dioxide in a solution of potassium 
hydroxide, the water in calcium chloride, and weighed. From 
the weights of the products the weights of carbon and hydrogen 
are calculated. Oxygen, if present, is not estimated directly, 
but by difference, i.e., the weights of carbon and hydrogen found 
are added together, and the sum subtracted from the weight of 
the original substance. The difference represents the weight 
of the oxygen. 

A detailed description of the apparatus and of the method of 
procedure need not be given here, as it can be found in any 
book on analytical chemistry. A brief description, however, 
ma}' not be out of place. The combustion is effected in a hard 
glass tube which is heated by means of a gas furnace con- 
structed for the purpose. Ordinarily, the substance is placed 
in a narrow porcelain or platinum vessel, called a boat, which is 
introduced into the tube with granulated copper oxide. The 



ANALYSIS. 11 

tube is then connected with (1) a U-tube filled with calcium 
chloride ; (2) a set of bulbs containing a solution of potassium 
hydroxide, and constructed so as to secure thorough contact of 
the passing gases with the solution ; and (3) a small U-tube 
filled with solid potassium hydroxide. After the combustion is 
completed, a current of pure dry oxygen is passed through the 
tube ; and, finally, air is passed until the oxygen is displaced. 
The method at present used was devised by Liebig. It has 
contributed very greatly to a thorough understanding of the 
compounds of carbon. 

Two methods are in common use for the estimation of nitrogen 
in carbon compounds. The first is known as the absolute method. 
This consists in oxidizing the substance by means of copper 
oxide ; then decomposing, by means of highly-heated metallic 
copper, any oxides of nitrogen which may have been formed, 
and collecting the nitrogen. The volume of the nitrogen thus 
obtained is measured, and its weight easily calculated. The 
chief difficulty in this method consists in removing the nitrogen 
contained in the apparatus before the combustion is made. 
The simplest way is to pass pure carbon dioxide through the 
apparatus until the gas that passes out is completely absorbed 
by caustic potash. The combustion is then made by heating the 
tube containing the substance and copper oxide and a layer of 
copper foil ; and, finally, carbon dioxide is again passed through 
at the end of the operation. The only three gases which can be 
present, assuming that the substance contained nothing but car- 
bon, hydrogen, oxygen, and nitrogen, are carbon dioxide, water 
vapor, and free nitrogen. The water vapor is, oi' course, con- 
densed, and the carbon dioxide is absorbed by passing the gases 
through a. solution of potassium hydroxide, leaving the nitrogen 
thus alone. 

The second method for the estimation of nitrogen consists in 
heating the substance with a mixture of sodium hydroxide and 
quicklime, called soc&a-Kme, or with sulphuric acid and potas- 
sium permanganate. The nitrogen is thus converted into 



12 INTRODUCTION. 

ammonia, which is collected in a known quantity of dilute hydro- 
chloric or sulphuric acid. After the operation, the amount of 
acid remaining unneutralized is determined by titration ; and 
from this the amount of ammonia formed can be calculated; and 
from this, in turn, the amount of nitrogen. This method is not 
applicable to all compounds, because the nitrogen of some com- 
pounds is not converted into ammonia under the circumstances 
mentioned. The method based upon the use of sulphuric acid 
and potassium permanganate, known as the Kjeldahl method, 
is now used almost to the exclusion of other methods. 

In regard to the estimation of other constituents of carbon 
compounds, it need only be said that in most cases it is neces- 
sary to get rid of the carbon and hydrogen by some oxidizing 
process before the estimation can be made. Thus, in estimating 
sulphur, it is customary to fuse the substance with potassium 
nitrate and hydroxide, when the carbon and hydrogen are 
oxidized, and the sulphur is left in the form of potassium sul- 
phate, and can be estimated in the usual way. 

Formula. — The deduction of the formula of a compound 
from the results of the analysis involves two steps. The first is 
a matter of simple calculation. It is assumed that students who 
use this book are already familiar with the method of calculating 
the formula from the analytical results ; but an example will, 
nevertheless, be given. Suppose that the analysis has shown that 
the substance contains 52.18 per cent carbon, 13.04 per cent hy- 
drogen, and 34.78 per cent oxygen. To get the atomic propor- 
tions, divide the figures representing the percentages of the 
elements by the corresponding atomic weights. We have thus: 

Percentage. At. Wt, Kelative JsTo. of Atoms. 

12 = 4.35 - 2 
1 = 13.04 - 6 

16 = 2.17 - 1 
That is to say, accepting the atomic weights, 12 for carbon and 
16 for oxygen, the simplest figures representing the number of 
atoms of the three elements in the compound are 2 for carbon, 



c 


52.18 


H 


13.04 





34.78 



FORMULA. 13 

6 for lrydrogen, and 1 for oxygen. According to this, the 
simplest formula that can be assigned to a substance giving 
the above results on analysis is C 2 H 6 0. But the formula 
C 4 H 12 2 is equally in accordance with the analytical results, and 
we can only decide between the two by determining the molecular 
weight. This, as is known, is done by determining the specific 
gravity of the substance in the form of vapor. This operation 
is of the greatest importance. It is assumed that the student, 
who has already studied the elements of inorganic chemistry, is 
familiar with it, and with the exact connection that exists 
between it and the molecular weight of the compound. A few 
statements in regard to the connection will, however, be made 
here, in order to recall its chief points, and to impress upon the 
mind of the student its fundamental importance. 

Every chemical formula is intended to represent the molecule 
of a compound and the composition of the molecule. Our 
conception of the molecule is based almost exclusively on 
Avogadro's hypothesis, according to which equal volumes of all 
gases contain the same number of molecules. Hence, lry com- 
paring equal volumes of bodies in the form of gas or vapor, we 
get figures which bear to each other the same relations as the 
weights of the molecules. The figures called the specific gravi- 
ties express the relations between the weights of equal volumes. 
In the case of gases, air is taken as the standard, and the 
weights cf other gases are compared with this standard. Thus, if 
we say that the specific gravity of a gas is 0.918, we mean thai 
if we call the weight of any volume of air 1. that of the sam \ 
volume of the other gas measured under the same conditions < 
temperature and pressure is 0.918. If we assign to any 
pound a certain molecular weight, the molecular weights of other 
gaseous compounds can be determined without difficulty. We 
must, therefore, Brst select some substance, the molecule of 
which may be used as the standard. Hydrochloric acid is 
commonly taken, because hydrogen and chlorine unite with 

each other in only one proportion, and there is good evidence 



14 INTRODUCTION. 

in favor of the view that it represents the simplest kind of 
combination, viz., that of one atom of one element with one of 
another. Hydrogen and chlorine are present in the compound 
in the proportion of 1 part of hydrogen to 35.4 parts of chlorine ; 
hence the simplest molecular weight that can be assigned to 
the compound, the atomic weight of hydrogen being 1, is 36.4. 
The molecular weight of this standard molecule is, therefore, 
taken to be 36.4, and we have now simply to compare the 
weights of other gases with that of hydrochloric acid in order 
to know their molecular weights. Thus, to illustrate by means 
of the body whose atomic relations we found by analysis to be 
represented by the formulas C 2 H 6 0, C^H^CX, etc., if this body 
be converted into vapor and its specific gravity determined, it 
might be found to be 1.6. The relation between the molecular 
weight of any body and its specific gravity is expressed by the 
equation 

M = d X 28.88, 

in which M is the molecular weight, and d the specific gravity 
of the substance in the form of gas or vapor. As d is 1.6 in 
the case under consideration, we have 

M (the unknown molecular weight) = 1.6 X 28.88 = 46.2. 

If the formula of the compound is C 2 H 6 0, the molecular weight, 
being the sum of the weights of the constituent atoms, is 

2 X 12 + 6 X 1 + 16 = 46, 

which agrees with the figure deduced from the specific gravity. 
It therefore follows that the formula C 2 H 6 is correct. 

There are some other methods which may be used in deter- 
mining the molecular weight of a compound. Among these 
may be mentioned the analysis of salts. To illustrate this, 
take the case of acetic acid. Analysis shows us that it must be 
represented by one of the formulas CH 2 0, C 2 H 4 2 , C 3 H 6 2 , etc. 
If we make the silver salt, we find that its analysis leads us to 
the formula C 2 H 3 2 Ag, and not CHOAg, and we hence conclude 
that the molecular formula of acetic acid is C 2 H 4 2 . 



STRUCTURAL FORMULA. 15 

The molecular weight of a substance can also be determined 
by means of observations on the boiling-points and freezing- 
points of its solutions. The general facts underlying these 
determinations are that, in the case of any given solvent, 
solutions containing the same number of molecules have the 
same boiling-point; and, in the same way, in the case of any 
given solvent, solutions containing the same number of mole- 
cules have the same freezing-point. By knowing the weight 
of the substance dissolved, the weight of the solvent, and the rise 
in boiling-point caused by the substance, together with certain 
facts in regard to the solvent, it is possible to draw a conclu- 
sion in regard to the molecular weight of the substance. The 
same is true in regard to the freezing-point. The change 
effected in this case is a lowering of the freezing-point. 

Structural formula. — The formulas C 2 H 6 2 , C 2 H 4 2 , C 3 H 8 , 
etc., tell us simply the composition of the three compounds repre- 
sented, and tell us also the relative weights of their molecules. 
In studying the chemical conduct of these compounds, their 
decompositions, and the modes of preparing them, we become 
familiar with many facts which it is desirable to represent by 
means of the formulas. Thus, for example, but one of the four 
atoms of hydrogen represented in the formula of acetic acid, 
C 2 H 4 2 , can be replaced by metals. It plainly differs from the 
three remaining atoms, and it is natural to conclude that it is held 
in the molecule in some way differently from the other three. We 
may, therefore, write the formula (\, I l.O.,.l 1, which is intended to 
call attention to the difference. By further study of acet ie acid, 
we find that that particular hydrogen, which gives to it its acid 
properties, and which, in the above formula, is written by itself, 
is intimately associated with oxygen. It can be removed with 
oxygen by very simple reactions, and the place of both taken 
by one atom of some other element; as. for example, chlorine. 
Thus, when acetic acid is treated with phosphorus trichloride, 
PC1 S , it is converted into acetyl chloride, C..ll :; OCl, according to 
this equation : — 



16 INTRODUCTION. 

3 C 2 H 4 2 + PC1 3 = 3 C 2 H 3 0C1 + PO3H3. 

The result of the action is the direct substitution of one atom 

of chlorine for one atom of hydrogen and one atom of oxygen 

in acetic acid, a fact which points to an intimate connection 

between the hydrogen and oxygen in the acid. Further, 

when acetyl chloride is heated with water, acetic acid is 

regenerated, hydrogen and oxygen from the water entering 

into the place occupied by the chlorine, as represented in this 

equation : — 

C 2 H 3 0C1 + H 2 = C 2 H 4 2 + HC1. 

From facts of this kind the conclusion is drawn that in acetic 
acid hydrogen and oxygen are connected; or, as it is said, linked 
together ; and this conclusion is represented in chemical lan- 
guage by the formula C 2 H 3 O.OH, which may serve as a simple 
illustration of what are called structural or constitutional for- 
mulas. In all compounds the attempt is made, by means of a 
thorough study of the conduct of the compounds, to trace out 
the connections existing between the constituent atoms. When 
this can be done for all the atoms contained in a molecule, the 
structure or constitution of the molecule or of the compound is 
said to be determined. The structural formulas which have 
been determined by proper methods have proved of much value 
in dealing with chemical reactions, as they enable the chemist 
who understands the language in which they are written to see 
relations which might easily escape his attention without their 
aid. In order to understand them, however, the student must 
have a knowledge of the reactions upon which they are based ; 
and he is warned not to accept any chemical formula unless he 
can see the reasons for accepting it. He should ask the question, 
upon what facts is it based ? whenever a formula is presented for 
the first time. If he does this conscientiously, he will soon be 
able to use the language intelligently, and the beauty of the 
relations which exist between the large number of compounds 
of carbon will be revealed to him. If he does not, his mind 
will soon be in a hopeless muddle, and what he learns will be 



CLASSIFICATION OF COMPOUNDS OF CARBON. 17 

of little value. For the beginner, this advice is of vital im- 
portance : Study with great care the reactions of compounds ; 
study the methods of making them, and the decompositions which 
they undergo. The formulas are but the condensed expressions 
of the conclusions which are drawn from the reactions. 

General principle of classification of the compounds 
of carbon. — In considering the elements and compounds in- 
cluded under the head of Inorganic Chemistry, the fundamental 
substances are, of course, the elements. The properties of the 
elements enable us to separate them, for study, into a number 
of groups ; as, for example, the chlorine group, including 
bromine, iodine, and fluorine; the oxygen group, in which 
are included sulphur, selenium, and tellurium. To recall the 
method generally adopted, let us take the chlorine group. 
In studying the members of this group, there is found great 
similarity in their properties. Their hydrogen compounds next 
present themselves, and here the same similarity is met with. 
Then, in turn, the oxygen and the oxygen and hydrogen com- 
pounds are considered, and again the resemblances in properties 
between the corresponding compounds of chlorine, bromine, and 
iodine are met with. We thus have groups of elements, and 
of the derivatives of these elements, as, — 

CI C1H CIO3H 

Br BrH Br0 8 H 

I IH E0 8 H, etc. 

Of course, the chlorine group is quite distinct from the oxygen 
group and from all other groups; and each member of the 
chlorine group is, at least so Ear as we know, quite independent 
of the other members. We cannot make a bromine compound 
from a chlorine compound, nor a chlorine compound from a 
bromine compound, without directly substituting the one ele- 
ment for the oilier. 

Now, when we come to study the compounds of carbon, we 
shall find that the same general principle oi classification is 



18 INTRODUCTION. 

made use of; only, in consequence of the peculiarities of the 
compounds, the system can be carried out much more perfectly ; 
the members of the same group can be transformed one into 
the other, and it is also possible to pass from one group to 
another by means of comparatively simple reactions. 

The simplest compounds of carbon are those which contain 
only hydrogen and carbon, or the hydrocarbons. All the other 
compounds may be regarded as derivatives of the hydrocarbons. 
To begin with, there are several groups or series of hydrocar- 
bons, which correspond somewhat to the different groups of 
elements. The members of one and the same series of hydro- 
carbons resemble one another more closely than the members of 
one and the same series of elements. Although we have indica- 
tions of the existence of more than ten series of these hydrocar- 
bons, only three or four of the series are at all well known, and 
of these, but two include more than two or three members that 
need to be considered in this book. 

Starting with any series of hydrocarbons, several classes of 
derivatives can be obtained by treating the fundamental com- 
pounds with different reagents. The chief classes of these 
derivatives are : (1) those containing halogens ; (2) those con- 
taining oxygen, among which are the acids, alcohols, ethers, etc. ; 
(3) those containing sulphur ; and (4) those containing nitrogen. 
Corresponding to every hydrocarbon, then, we may expect tofinl 
representatives of these different classes of derivatives. But the 
relations existing between any hydrocarbon and its derivatives 
are the same as those existing between any other hydrocarbon 
and its derivatives. Hence, if we know what derivatives one 
hydrocarbon can yield, we know what derivatives we may expect 
to find in the case of every other hydrocarbon. The student 
who, for the first time, undertakes the study of the chemistry 
of the compounds, is apt to feel overwhelmed by the enormous 
number of compounds described in the book or by the lecturer. 
This large number is really not a serious matter. No one is 
expected to become acquainted with every compound. A great 



CLASSIFICATION OF COMPOUNDS OF CARBON. 19 

many of these need only be referred to for the purpose of indicat- 
ing the extent to which the series to which they belong have been 
developed. In general, the members of any series so closely 
resemble one another, that, if we understand the simpler mem- 
bers, we have a fair knowledge of the more complicated members. 

It is proposed, in this book, to treat only of the more im- 
portant compounds and the more important reactions, the 
object being ratjier to give a clear, general notion of the subject 
than detailed information regarding particular compounds. 
Should the student desire more specific information concerning 
the properties of any of the compounds mentioned, he can 
easily find it in some larger book. It will, however, hardly 
be profitable for him, at the outset, to burden his mind with 
details. He may thereby sacrifice the general view, which it 
is so important that he should gain as quickly as possible. 

The plan which will be followed is briefly this : Of the first 
series of hydrocarbons two members will be treated of. Then 
the derivatives of these two will be taken up. These deriva- 
tives will serve admirably as representatives of the correspond- 
ing derivatives of other hydrocarbons of the same series, and of 
other series. Their characteristics and their relations to the 
hydrocarbons will be dwelt upon, as well as their relations to 
each other. Thus, by a comparatively close study of two hydro- 
carbons and their derivatives, we may acquire a knowledge of the 
principal classes of the compounds of carbon. After these typical 
derivatives have been discussed, the entire series of hydrocar- 
bons will be taken up briefly, only such facts being dealt with 
at all fully as are not illustrated by the first two members. 

After the first series has been studied in this way, and a clear 
idea of the relations between the various classes has been 
obtained, a second series will be taken up ami treat ml in a 
similar way, and so on. But, as already stated, only a few oi' 
the series require very much attention at the beginning. The 
first series which will be used for the purpose of illustrating the 
general principles is one o\' the tiro most important series, ami 
of the only two that need be taken up at all fully at present, 



CHAPTER II. 

METHANE AND ETHANE. -HOMOLOGOUS 
SERIES. 

If we were to study all the hydrocarbons known, and were 
then to arrange them in groups according to their properties, 
we should find that a large number of them resemble marsh gas 
in their general conduct. Some of the points of resemblance 
are these : They are very stable, resisting with marked power 
the action of most reagents ; and nothing can be added to t^em 
directly, — if any change takes place in them, hydrogen is first 
given up. On arranging these substances according to the 
number of carbon atoms contained in them, we have a remark- 
able series, the first six members of which, together with their 
formulas, are included in the subjoined table : — 

Methane (or Marsh Gas) CH 4 . 

Ethane C 2 H6. 

Propane C 3 H 8 . 

Butane C 4 H 10 . 

Pentane . QH^. 

Hexane C 6 H 14 . 

On examining the formulas given, we see that the difference in 
composition between any two consecutive members is represent-', i 
by CH-v,. Thus, adding CH 2 to marsh gas, CH 4 , we get ethane. 
C 2 H 6 ; adding CH 2 to C 2 H 6 , we get C 3 H 8 , and so on, in each 
successive step. Any series of this kind, in which the succes- 
sive members increase in complexity by CH 2 , is called an homol- 
ogous series. 

Just as the members of an homologous series of hydrocarbons 



, 



METHANE AND ETHANE. 21 

differ from one another by CH 2 , or some multiple of it, so 
also the members of any class of derivatives of these hydro- 
carbons differ from one another in the same way, and form 
homologous series. Thus, running parallel to the hydrocarbons 
mentioned above, there are two homologous series of oxygen 
derivatives, as indicated below: — 

CH 4 -CH 4 -CHA- 
G 2 H 6 -C 2 H 6 -C 2 H 4 2 . &z 
C 3 -R £ - C 3 H 8 - C 3 H 6 2 . 

C 4 H 10 -C 4 H 10 O-C 4 H 8 O 2 . 
C 5 H 12 -C 5 H 12 O-G 5 H 10 O,. 
C 6 H 14 — C 6 H 14 — C (; H 12 2 . \ 

The relation observed between the members of the homologous 
series mentioned is by no means a peculiarity of the marsh 
gas series of hydrocarbons and of their derivatives, but is 
observed in the case of all other series of hydrocarbons and 
their derivatives. 

Strictly speaking, there is perhaps no analogy for this re- 
markable fact among the elements and their compounds, yet 
facts which suggest analogy are known. Consider, for example, 
the chlorine series. We have 

Chlorine, with the atomic weight, 35.4 
Bromine, " " " 80. 

Iodine, " " " 127. 

Is is well known, the difference between (lie atomic weights o\' 
chlorine and bromine is approximately equal to the difference 
between those of bromine and iodine. En other words, there is 
a regular increase in complexity as we pass from chlorine to 
iodine. Or, at Least, there is a regular increase in the atomic 
weights of these similar elements, just as there is a regular 
increase in the molecular weights of the similar members o( an 
homologous series. While, however, a satisfactory hypothesis 



22 METHANE AND ETHANE. 

has been offered to account for the latter fact, and experi* 
mental evidence is strongly in favor of the hypothesis, no satis- 
factory explanation of the former has been offered ; or rather 
no satisfactory experimental evidence has been furnished in 
favor of the various hypotheses which from time to time have 
been put forward to account for the similarity between members 
of the same group of elements. 

The view at present held in regard to the nature of homology 
is founded, primarily, upon the idea that carbon is quadrivalent. 
If carbon is quadrivalent, it of course follows that the com- 
pound, marsh gas, CH 4 , is saturated ; that is, the molecule 
cannot take up anything without losing hydrogen. In order, 
therefore, that we may get a compound containing two atoms 
of carbon in the molecule, some of the hydrogen must first be 
given up. With our present views, we cannot conceive of union 
taking place directly between the molecules CH 4 and CH 4 , but 
we can conceive of union taking place between the molecules 
CH 3 and CH 3 , to form a molecule C 2 H 6 , which in turn is satu- 
rated. Representing graphically what is believed to take 
place, we have, first, marsh gas, which we may represent thus, 

H 

I 
H — C — H. If this loses one atom of hydrogen, we have the 

I . H 

H I 

unsaturated residue H — C — , which is capable of uniting with 

H 

another molecule of the same kind to form the more complex 

H H 

I I 
molecule H — C — C — H, or C 2 H 6 , which is believed to express 

H H 
the relation existing between marsh gas, CH 4 , and ethane, C 2 H 6 , 
or between any two adjoining members of an homologous series. 
The evidence in favor of this view will be presented when the 
reactions by means of which the hydrocarbons are made 
are discussed. The explanation offered, and now generally 



METHANE (MARSH GAS, FIRE DAMP). . 23 

accepted, involves the idea that carbon atoms have the power 
of uniting with each other. And, as the explanation for the 
relation between the first and second members is, in principle, 
the same as for the relation between the second and third, the 
third and fourth, etc., it appears that this power of carbon atoms 
to unite with one another is very extensive. It is to the power 
which carbon possesses of forming homologous series, or to the 
power of the atoms of carbon to unite with each other, that we 
owe the large number of compounds of this element. 

Methane (marsh gas, fire damp), CH^. — This hydro- 
carbon is found rising from pools of stagnant water in marshy 
districts. If a bottle is filled with water and inverted with a 
funnel in its neck in such a pool, some of the gas can be col- 
lected by holding the funnel over the bubbles rising from the 
bottom. It is also found in large quantities mixed with air, in 
coal mines, and sometimes issues from the earth, together 
with other gases, in the neighborhood of petroleum wells. 

It can be prepared by treating aluminium carbide, a com- 
pound of aluminium and carbon of the formula, C3AI4, with 
water as represented in the equation : — 

C 3 A1 4 + 12 H 2 = 3 CH 4 + 4 Al (OH) 3 . 

This method is of special interest for the reason that it indi- 
cates the possibility of making marsh gas from the elements ; 
aluminium carbide and water being made readily from the 
elements. 

It is formed, as its occurrence in marshes indicates, by the 
decomposition of organic matter under water. In pure condi- 
tion it is made most readily by mixing 2 parts sodium acetate, 
2 parts potassium hydroxide, and 3 parts quicklime, and heat- 
ing the mixture. Writing sodium instead oi' potassium hydrox- 
ide, the action which takes place is represented thus: — 

NaC 2 H 3 0, + NaOll = CH< + Na.(H\, 



24 METHANE AND ETHANE. 

It will be shown hereafter that most acids of carbon break up 
in a similar way, yielding a hydrocarbon and a carbonate. 

Properties. Marsh gas is colorless and inodorous. It is 
slightly soluble in water, but not so much so as to prevent its 
collection over water. It burns. Its mixture with air is explo- 
sive. It is this mixture which is the cause of the explosions 
which so frequently take place in coal mines. 

Experiment 3. Make marsh gas from dehydrated sodium acetate, 
potassium hydroxide, and calcium oxide, using the substances in the pro- 
portion stated on the preceding page. Dehydrate some sodium acetate by 
heating it in a porcelain dish on wire gauze over a small flame. Use 
10e of sodium acetate. Collect the gas over water. Burn some as it es- 
capes from a jet. In small quantities it does not readily explode with air. 

Reagents, in general, do not act readily upon marsh gas. 
Chlorine in diffused daylight gradually takes the place of the 
hydrogen, forming a series of compounds which will be treated 
of under the head of the halogen derivatives of methane. The 
simplest of them has the composition represented by the formula 
CH3CI, and is known as chlor-methane or methyl chloride. 

Ethane, C2H6. — Ethane rises from the earth from some of 
the gas wells in the regions in which petroleum occurs. It is 
also found dissolved in crude petroleum. 

It can be made from methane by introducing a halogen and 
making a compound like chlor-methane, CH 3 C1. As the corre- 
sponding iodine derivative is less volatile, it is used. This iodo- 
methane, CH 3 I, is treated with zinc or sodium in some neutral 
medium, as, for example, anhydrous ether. The reaction which 
takes place is represented thus : — 

CH 3 I + CH3I + 2 Na = C 2 H 6 + 2 Nal. 

This method of building up more complex from simpler hydro- 
carbons has been used extensively; and it is well adapted to 
showing the relations between the substances formed and the 
simpler ones from which they are made. 

An operation of the kind involved in the above-mentioned 



ETHANE. 25 

preparation of ethane is called a synthesis. The essential feature 
of the synthesis is the formation of a more complex substance from 
simpler ones. Our knowledge of the structure of the compounds 
of carbon is largely dependent upon the use of various methods 
of synthesis. For example, in the case under consideration, the 
synthesis gives us at once a clear view of the relations between 
ethane and. methane, and also suggests that homology may be 
due to similar relations between the successive members of the 
series, — a view which is fully confirmed by the synthetical prep- 
aration of the higher members. A similar method of synthesis 
has been used in the preparation of tetrathionic acid from 
sodium thiosulphate. The action is represented thus: — 



Na 2 S 2 3 1 + ^ = NaSA > + 2 NftL 



Na 9 S 9 0j NaS 9 Oc 



Two mol. sodium Sodium tetra. 

tMosulphate. thionate. 



CHAPTER III. 

HALOGEN DERIVATIVES OP METHANE 
AND ETHANE. 

Substitution. — When methane and chlorine are brought 
together in diffused daylight, action takes place gradually ; 
hydrochloric acid gas is given off, and one or more products 
are obtained, according to the length of time the action con- 
tinues. The products have been studied carefully, and four 
have been isolated. The composition of these products is repre- 
sented by the formulas CH 3 C1, CH 2 C1 2 , CHC1 3 , and CC1 4 . We 
see thus that the action of chlorine consists in replacing, step 
by step, the hydrogen of the hydrocarbon. The action is repre- 
sented by the four equations : — 

(1) CH 4 + Cl 2 = CH3CI + HC1; 

(2) CH3CI + Cl 2 = CH 2 C1 2 -f HC1 ; 

(3) CH 2 C1 2 + Cl 2 = CHCI3 + HC1 ; 

(4) CHClg + CI, = CC1 4 + HC1. 

This replacement of hydrogen by chlorine is an example of 
what is known as substitution. We shall find that most hydro- 
carbons are very susceptible to the influence of the halogens 
and a number of other reagents, such as nitric acid, sulphuric 
acid, etc., and that thus a large number of derivatives can be 
made, differing from the hydrocarbons in that they contain one or 
more halogen atoms or complex groups in the place of the same 
number of hydrogen atoms. It must be borne in mind that the 
mere fact that chlorine, in acting upon marsh gas, is substituted 
for an equivalent quantity of hydrogen, does not prove that 



DI-IODO-METHANE. 27 

the chlorine in the product occupies the same place that the 
replaced hydrogen did. Nevertheless, a careful study of all 
the facts regarding the products thus formed has led to the 
belief that the substituting atom or residue does occupy the 
same place, or bear the same relation to the carbon atom as 
the hydrogen did. 

The name substitution-products properly includes all products 
made from the hydrocarbons, or from other carbon compounds, 
by the substitution process. The principal ones are those 
formed by the action of the halogens, or the halogen substitution- 
products; those formed by the action of nitric acid, or the nitro- 
substitution-products ; and those formed by the action of sulphuric 
acid, or the sulphonic acids. The last are, however, not com- 
monly called substitution-products. 

Chlor-methane, methyl chloride, CH 3 C1. 

Brom-methane, methyl bromide, CH : .Br. 

Iodo-methane, methyl iodide, CH.J. 

The chlorine and bromine products can be made by treating 
methane with the corresponding element. They can be most 
easily made by treating methyl alcohol with the corresponding 
hydrogen acids : — 

CH 4 f HC1 = CH3CI + H,0. 

Methyl alcohol. Chlor-methane. 

Di-iodo-methane, methylene iodide, CHJ,.. — This sub- 
stance is the principal halogen derivative of methane containing 
two halogen atoms. It is made from iodoform or tri-iodo- 
111 ethane, CHT 3 ,- by treating it with hydriodic acid, the latter 
acting as a reducing agent: — 

CHI 3 + HI = ni.,L + \ t 

As will be seen, this is a case of rcrersc substitution; in other 
words, the action is the opposite of that described above as 
substitution. Methylene iodide is a liquid that boils at L80°, 
and has the specific gravity 3.342, 



28 DERIVATIVES OF METHANE AND ETHANE. 

Chloroform, CHC1 3 . -\ The best known and most exten- 
Bromoform, CHBr 3 . > sively used of these three derivatives 
Iodoform, CHI 3 . 3 is chloroform or tri-chlor-methane. It 
is made by treating alcohol or acetone with "bleaching powder." 
The action is deep-seated, involving at least three different 
stages. It will be treated of more fully under the head of 
chloral (which see). Chloroform is a heavy liquid of specific 
gravity 1.526. It has an ethereal odor, and a somewhat sweet 
taste. It is scarcely soluble in water. It boils at 62°. It is 
one of the most valuable anaesthetics, though there is some 
danger attending its use. 

Experiment 4. Mix 550§" bleaching powder and 1} litres water in 
a 3-litre flask. Add 33s alcohol of sp. gr. 0.834. Heat gently on a water- 
bath until action begins. A mixture of alcohol, water, and chloroform 
will distil over. Add water, and remove the chloroform by means of 
a pipette. Add calcium chloride to the chloroform, and, after standing, 
distil on a water-bath. 

Iodoform, which is used extensively in surgery, is made 
by bringing together alcohol, an alkali, and iodine. It is a 
solid substance, soluble in alcohol and ether, but insoluble in 
water. It crystallizes in delicate, six-sided, yellow plates. 
Melting-point, 119°. 

Experiment 5. Dissolve 20=" crystallized sodium carbonate in 100= 
water. Pour 10=" alcohol into the solution, and, after heating to 60° 
to 80°, gradually add 10= iodine. The iodoform separates from the 
solution. 

Tetra-chlor-methane, CC1 4 , is made by treating carbon disul- 
phide with chlorine, and by treating chloroform with iodine 
chloride, IC1. 

Equivalence of the hydrogen atoms in methane. Having thus 
seen that the hydrogen atoms of methane can easily be replaced, 
the interesting question suggests itself whether these hydrogen 
atoms all bear the same relation to the carbon atom. We 
accept the conclusion that the carbon atom is quadrivalent, 



IODOETHANE. 29 

and that each of the four hydrogen atoms is in combination 

H(l) 
I 
with it, as indicated in the formula (4)H — C— H(2). Do the 

I 
H(8) 

atoms numbered 1, 2, 3, and 4 bear the same relation to the 
carbon or not? If they do not, then, on replacing H (1) by 
chlorine, the product should be different from that obtained by 
replacing H (2), H (3), or H (4) ; or, it should be possible 
to make more than one variety of chlor-methane and of similar 
products. This subject is an extremely difficult one to deal 
with. It can only be said that, although chlor-methane has 
been made in several ways, the product obtained is always 
the same one ; and the same is true of all other substitution- 
products of methane. Hence, ive have no reason whatever for 
believing that there are any differences between the hydrogen 
atoms of methane. We therefore conclude that they all bear the 
same relation to the carbon atom. 

This conclusion is of fundamental importance in dealing with 
the higher members of the methane series, and, indeed, in deal- 
ing with all carbon compounds, as will be seen later. 



Chlor-ethane, ethyl chloride, C 2 H 5 C1. 

Brom-ethane, ethyl bromide, C 2 H 5 Br. 

Iodo-ethane, ethyl iodide, C.H 5 I. 

These substances are all liquids having pleasant ethereal odors. 
The first boils at 12°, the second at 38.8°, and the third at 72°. 
They are 111() ^,r^Wv_m^d£^fr^)ni alcohol, by treating with the 
Corresponding hydrogen acids. In the ease of the bromide and 
iodide, ifr~is simpler to treat the alcohol with red phosphorus 
and the halogen. The action is similar to that involved in 
making hydrobromic acid by treating water with red phosphorus 
and bromine. It will be shown that alcohol is a hydroxide, 
in which hydroxy] (Oil) is in combination with the group (11.. 
called ethyl, as represented in the formula (.\.H : ,.Ol I. When 



30 



DERIVATIVES OF METHANE AND ETHANE. 



bromine is brought in contact with red phosphorus, the tribro* 
mide, PBr 3 , is formed, and this acts upon the alcohol thus : — 

C 2 H 5 .OH Brl 

C 2 H 5 .OH + Br L P = 3 C 2 H 5 Br -f P(OH) 8 . 

C 2 H 5 .OH Br J 

When water is used instead of alcohol, the bromine appears ii 
combination with hydrogen as hydrobromic acid. 

Experiment 6. Arrange an apparatus as represented in Fig. 4. 
In the flask place 10s red phosphorus and 60s absolute alcohol. Put 
60s bromine in the glass-stoppered funnel, and, by means of the stop- 




Fig. 4. 

cock, let the bromine enter the flask very slowly, drop by drop. After 
allowing the mixture to stand for two or three hours, gently heat the 
water-bath, and the brom-ethane will distil over. Place the distillate in 
a glass-stoppered cylinder, and shake it first with water to which some 
caustic soda has been added, and then two or three times with water 
alone. Separate the water from the brom-ethane either by means of a 
pipette 1 or a separating funnel. Add two or three pieces of fused 

1 A good pipette for separating two liquids of different specific gravities can be easily 
made as follows: Select a piece of glass tubing about 1.5 to 2 cm internal diameter, and a 



ISOMERISM. 31 

calcium chloride the size of a small marble, and let stand for a few 
hours. Then pour off into a clean, dry distilling bulb, and distil, noting 
the boiling-point. 

Among the many halogen substitution-products of ethane 
containing more than one halogen atom, only two will be men- 
tioned. These are the two di-cJilor-ethanes, both of which are 
represented by the formula C 2 H 4 C1 2 . The existence cf these 
two substances, having the same composition but entirely differ- 
ent properties, affords a good example of what is known as 
isomerism. 

Isomerism. — One of the most striking and interesting facts 
with which we become familiar in studying carbon compounds, 
is the frequent occurrence of two, and often more, substances 
containing the same elements in the same proportions by weight. 
Substances which bear this relation to one another are said to 
be isomeric. 

Isomerism is of two kinds : (1) Substances may have the same 
percentage composition and the same molecular weights. Such 
bodies are said to be metameric. The di-chlor-ethanes, C 2 H 4 C1 2 , 
for example, are metameric. (2) Substances which have the same 
percentage composition but different molecular weights are said 
to be polymeric. Acetylene, C 2 H 2 , benzene, C 6 H 6 , and styrene, 
C 8 H 8 , are polymeric. 

second that will fit snugly into it, so that it can be moved up and down without difficulty. 
Draw out the larger tube, and fit to it a tube of about 6 mn > diameter and 16"" long. 
Then draw out this last tube to a small opening. Close the smaller of the two large tubes 
by melting it together. Finally, put this tube into the largest one, and draw over the two 
a broad piece of thick rubber tubing, which will close the opening between the two. and 
tit the same time permit the upward and downward movement of the smaller tube. The 
pipette has the form represented in Fig. 5. 



Pig. ;>. 

The dimensions may be varied, but the following will be found convenient : length of 
widest tube about 16 to 20 MB J total length of inner tube, or piston, about 25 to 80«, In- 
stead of drawing the large tube out and fitting the smaller lube to it. the union ma] he 
made by meana of a cork. 



82 DERIVATIVES OF METHANE AND ETHANE. 

The cause of isomerism is undoubtedly to be found in the 
different relations which the parts of isomeric compounds bear 
to each other. Our structural formulas, which show the relations 
between the parts of compounds which have been traced out by 
a study of the chemical conduct of these compounds, give us an 
insight into the causes of isomerism. To illustrate, let us take 
the two di-chlor-ethanes. One of these is made by treating 
ethane, the other by treating ethylene, C 2 H 4 , with chlorine. 
In the first case the action is substitution ; in the second, the 
chlorine is added directly to ethylene, thus, — 

G2H4 -f- CI9 == G 2 H.4C1 2 . 

The product from ethylene is called ethylene chloride; that from 
ethane, ethylidene chloride. It will be shown that ethylene is to 

CH 2 
be represented by the formula i ; that is, that in it two hydro- 

CH 2 

gen atoms are in combination with each of the carbon atoms. 

Now, if chlorine is brought in contact with this substance, we 

should naturally expect each of the carbon atoms to take up one 

atom of chlorine, and thus to become saturated, as represented 

in the equation, — 

CH 2 CI CH 2 C1 

I + = I 

CH 2 CI CH 2 C1. 

Chlorine is taken up, and it is believed that the etlrylene 
chloride obtained has the structure represented by the formula 

CH 2 C1 

I , the distinctive feature of which is that each of the chlorine 

CH 2 C1 

atoms is in combination with a different carbon atom. 

We, however, can conceive of another possibility ; viz., that 
the chlorine atoms are both in combination with the same 

CHC1 2 
carbon atom, as represented in the formula | , and we 



should be inclined to the view that this represents the structure 



ISOMERISM. 33 

of ethylidene chloride. Fortunately we have experimental evi- 
dence to support this view. It will be shown that aldehyde 

CHO 
lias the formula | . When aldehyde is treated with phos- 

phorus pentachloride, two chlorine atoms take the place of the 

oxygen. A product which must be represented by the formula 

CHC1 2 

I is formed, and this is identical with ethylidene chloride. 

CH 3 

Thus it will be seen that the difference between the two iso- 
meric compounds, ethylene chloride and ethylidene chloride, 
depends upon the fact that in the former the two chlorine 
atoms are in combination with different carbon atoms, while 
in the latter both chlorine atoms are in combination with the 
same carbon atom. 

General characteristics of the halogen derivatives of methane 
and ethane. The one characteristic to which it is desirable 
that special attention should be called is the condition of the 
halogens jn_tlre^compounds. In general, chlorine in combina- 
tion in organic compounds can be detected by means of silver 
nitrate, or when dissolved in water, these compounds are 
ionized. The halogen substitution products of the hydrocar- 
bons are not ionized by water, and the chlorine in them cannot 
be detected by means of silver nitrate in the ordinary way. 
On the other hand, when chlor-m ethane is heated with a silver 
compound, the chlorine is removed. Sodium and zinc have the 
power of extracting the chlorine, bromine, etc., from halogen 
derivatives, and this fact is taken advantage of in the synthe- 
sis of many hydrocarbons. (See " Ethane," p. 24.) 



CHAPTER IV. 

OXYGEN DERIVATIVES OP METHANE 
AND ETHANE. 

There are several classes of oxygen derivatives of the hydro- 
carbons. Among them are the important compounds known as 
alcohols, ethers, aldehydes, and acids. Each of these classes 
will be taken up in turn. 

1. Alcohols. 

Among the most important ox}~gen derivatives are the alco- 
hols, of which methyl alcohol, or wood spirits, and ethyl alcohol, 
or spirits of wine, are the best known examples. As far as 
composition is concerned, these bodies bear very simple relations 
to the two hydrocarbons, methane and ethane. These rela- 
tions are indicated by the formulas, — 

Hydrocarbons. Alcohols. 

CH 4 CH 4 

C 2 H 6 C 2 H 6 0. 

The molecule of the alcohol differs from that of the correspond- 
ing Irydrocarbon by one atom of oxygen. In order to under- 
stand the chemical nature of alcohols, it will be best to study 
with some care the reactions of one ; and we may take for this 
purpose the simplest one of the series, methyl alcohol. 

Methyl alcohol, Methanol, CHtO. — This alcohol is also 
known as wood spirits. It is found in nature in combination in 
the oil of wintergreen. It is formed, together with many other 
substances, in the dry distillation of wood. It is hence contained 
in crude pyroligneous acid or wood vinegar. Wood is distilled 
in large quantities for various purposes ; chiefly, however, for 



METHYL ALCOHOL. 35 

making charcoal. In some charcoal factories the distillate is 
collected and utilized. Wood is distilled also for the purpose 
of making vinegar, or pure acetic acid. 

It is not an easy matter to get pure methyl alcohol from crude 
wood spirits. Fractional distillation alone will not answer ; 
though, if the mixture is distilled for some time, and the impure 
alcohol thus obtained then converted into some crystalline deriv- 
ative, the latter can be punned and then decomposed in such 
a way as to yield the alcohol in pure condition. 

Methyl alcohol is a liquid that boils at 66.7°, and has the 
specific gravity 0.8142 at 0°. It closely resembles ordinary 
alcohol in all its properties. It burns with a non-luminous 
flame. When taken into the system it intoxicates. In concen- 
trated form it is poisonous. It is an excellent solvent for fats, 
oils, resins, etc., and is extensively used for this purpose. 

1. Action of hydrochloric, hydrobromic, and other acids on 
methyl alcohol. The action of a few acids is represented by 
the following equations : — 

CH 4 -f HBr = CH 3 Br -f- H 2 ; 

CH 4 + HC1 = CH 3 C1 + HoO ; 

CH 4 + HNO3 = CH3NO3 -f- H 2 ; 

CH 4 + H 2 S0 4 = CH 3 .HS0 4 4- H 2 0. 

The action is plainly suggestive of that of metallic hydroxide's 
or bases. In each case, except the last, the acid is neutralized 
and water is formed, just as the acid would be neutralized by 
potassium hydroxide. 

2. Actipn of phosphorus trichloride. When phosphorus tri- 
chloride acts on methyl alcohol, the products are chlor-methane 
and phosphorous acid: — 

3 CH 4 4 IT!, = 3 CH 8 C] 4 l\OIl\, 

Here one atom of chlorine is substituted for an atom of hydro- 
gen, the reaction being like that which takes place between 
water and phosphorus trichloride: — 

3 H.,0 4 pci a = 3 uoi 4 i\om. 



36 DERIVATIVES OF METHANE AND ETHANE. 

This fact would lead us to suspect that there is some resem- 
blance between the alcohol and water. 

3. Action of potassium and sodium. When potassium is 
brought in contact with pure methyl alcohol, hydrogen is given 
off, and a compound containing potassium is formed : — 

CH 4 + K = CHgKO + H. 

Further treatment of this compound with potassium causes no fur- 
ther evolution of hydrogen, so that plainly one of the four hydro- 
gen atoms contained in methyl alcohol differs from the other three. 

The resemblance between methyl alcohol and metallic hy- 
droxides ; the substitution of chlorine for hydrogen and oxygen ; 
and the resemblance between the alcohol and water ; and, finally, 
the substitution of potassium for one, and only one, hydrogen 
atom, lead to the conclusion that the alcohol contains hydrogen 
and oxygen in combination, and that the characteristic reac- 
tions are due to the presence of the group called hydroxyl (OH). 
The analogy between the alcohol, a metallic hydroxide, and 
water is shown by these formulas : alcohol, CH 3 .OH; hydroxide, 
K.OH; water, H.OH. Thus water appears as. the type of both 
the hydroxide and the alcohol, and they may be regarded as 
derived from water by substituting the group CH 3 for one hydro- 
gen atom in the case of the alcohol, and substituting an atom 
of the metal potassium for one hydrogen atom in the case of 
the hydroxide. Or, on the other hand, methyl alcohol may be 
regarded as marsh gas in which one of the hydrogen atoms is 
replaced by hydroxyl. The two views are in fact identical. 

To test the correctness of the view, we may try to make 
methyl alcohol in some way that will show us of what parts it is 
made up. Thus, we may start with marsh gas, and introduce a 
halogen, as bromine. Now, if we bring brom-methane together 
with a metallic hydroxide, the bromine and the metal may 
unite, leaving the hydroxyl and the group CH 3 , which may 
unite also, as indicated in the equation 

CH 3 Br + MOH ~ CH3.OH + MBr, 



ETHYL ALCOHOL. 37 

If methyl alcohol could be made in this way, we should have very 
clear proof of the correctness of the view expressed in the formula 
CHg.OH. Methyl alcohol has been made by this reaction ; and 
it is indeed a general reaction for the preparation of alcohols, so 
that the proof that alcohols are hydroxides is conclusive. 

The reactions above presented show that the part of methyl 
alcohol that corresponds to the metal in the hydroxide is the 
group CH 3 . This it is which enters into the acids in place of 
their hydrogen, and this remains unchanged when potassium 
acts upon the alcohol. It has received the name methyl. Hence 
we have the names methyl alcohol, methyl bromide, methyl 
ether, etc. A group which, like methyl, appears in a number 
of compounds is called a radical, or residue. These names are 
intended simply to designate that part of a carbon compound 
which remains unchanged when the compound is subjected to 
various transforming influences. 

The two most characteristic reactions of methyl alcohol are : 
(1) its power to form salt-like compounds when treated with 
acids ; and (2) its power to form an acid when oxidized. 

The neutral compounds formed with acids correspond to the 
salts of metals, only they contain the radical, or residue, methyl, 
CH 3 , in the place of metals. They are called ethereal salts, or 
esters. 

The acid formed by oxidation has the composition expressed 
by the formula CHX> 2 . It contains one atom of oxygen more 
and two atoms of hydrogen less than the alcohol from which it is 
formed. It will be shown that this acid is the first of an impor- 
tant series of acids, known as the fatty acids, each of which bears 
the same relation to a hydrocarbon containing the same number 
of carbon atoms that this simplest acid bears to marsh gas. 

Ethyl alcohol, Bthanol, OaHs-OH. — This is the best 
known substance belonging to the class of alcohols. It is 
known also by the name spirits of wine and ordinary alcohol. 
It occurs in small quantities widely distributed in nature. 



38 DERIVATIVES OF METHANE AND ETHANE. 

The one method of preparation upor which we are dependent 
for alcohol is the fermentation of suga.. 

Fermentation. — Whenever a plant juice which contains 
sugar is left exposed to the air, it gradually undergoes a change 
by which it loses its sweet taste. Usually the change consists 
in a breaking up of the sugar into carbon dioxide and alcohol. 
The equation 

CeH^Oe = 2 C 2 H 6 + 2 C0 2 , 

Sugar. Alcohol. 

approximately expresses what takes place in the process which 
is known as alcoholic fermentation. It has been shown that 
fermentation is caused by the presence of small organized 
bodies, either animal or vegetable. These bodies, which are 
known as ferments, are of different kinds, and cause different 
kinds of fermentation with different products. Among the kinds 
of fermentation the following ma}' be specially mentioned : — 

1. Alcoholic or vinous fermentation. This is caused by a 
vegetable ferment which is contained in ordinary yeast. The 
ferment consists of small, round cells arranged in chains. The 
products of its action are alcohol and carbon dioxide. 

2. Lactic acid fermentation. This is due to a vegetable 
ferment which is contained in sour milk. It has the power of 
transforming sugar into lactic acid. 

3. Acetic acid fermentation. This is due to a peculiar vege- 
table ferment which acts upon alcohol, transforming it into 
acetic acid. 

The germs of various ferments are in the air ; and, when- 
ever they find favorable conditions, they develop and produce 
their characteristic effects. They will not develop in a solution 
of pure sugar. The variety of sugar which is fermentable, and 
which is the one from which alcohol is obtained, is not our 
ordinarj- cane sugar, but one known as grape sugar ; or, more 
commonly, glucose. In order that the ferments may grow, there 



FERMENTATION. l 39 

must be present in the solution, besides the sugar, substances 
which contain nitrogen. These, as well as the sugar, are con- 
tained in the juices pressed out from fruits, and hence these 
juices readily undergo fermentation. 

In the manufacture of alcohol a solution containing sugar is 
first prepared from the residue of wine presses, or from some 
kind of grain or potatoes. In case the solution contains grape 
sugar, this undergoes fermentation directly when the ferment 
is added. It the substance in solution is cane sugar, this 
is first changed by the ferment into grape sugar and fruit 
suo-ar, and the fermentation then takes place as in the first 
case. 

Experiment 7* Dissolve about 150s commercial grape sugar in 1 to 
1| litres of water in a good-sized flask. Connect the flask by means of 
a bent tube with a cylinder containing clear lime water. Protect the 
latter from the air by means of a tube containing caustic potash. Now 
add to the solution of grape sugar a little brewer's yeast; close the 
connections, and allow to stand. Soon an evolution of gas will begin, 
and, as this passes through the lime water, a precipitate of calcium 
carbonate will be formed. After the action is over, place the flask in 
a water-bath; connect with a condenser, and distil over 100 cc of the 
liquid. Examine this for alcohol. 

A good way to detect alcohol is this: Warm the solution to be 
tested ; add a small piece of iodine and then caustic potash until the 
color is destroyed. On cooling, a yellow crystalline powder of iodo- 
form is deposited. 

To obtain alcohol from fermented liquids, these must be dis- 
tilled. The ordinary alcohol contains water, and a mixture of 
other alcohols called fusel oil. The latter can be removed partly 
by distillation, and the last portions can be got rid of by filter- 
ing through charcoal. The water cannot be removed completely 
by distillation, though a product containing about 96 per cent 
of alcohol can be obtained in this way. 

Absolute alcohol is ordinary alcohol from which the water has 
been removed to a considerable extent by means of some dehy- 
drating agent, as quicklime, barium oxide, or anhydrous copper 



40 DERIVATIVES OF METHANE AND ETHANE. 

sulphate. By continued treatment with lime the quantity of 
water can be reduced to one-half a per cent, and this small 
quantity can be removed by treatment with metallic sodium. 

Experiment 8. Prepare absolute alcohol from ordinary strong 
alcohol. For this purpose a good-sized flask is one-half to two-thirds 
tilled with quicklime broken into small lumps. The alcohol is poured 
upon the lime, and allowed to stand at least twenty-four hours, when 
it is distilled off on a water-bath. If the alcohol used contains con- 
siderable water, it is necessary to repeat the treatment with lime. 

Pure ethyl alcohol has a peculiar, pleasant odor. It is 
claimed, however, that perfectly anhydrous alcohol has no 
odor. It remains liquid at very low temperatures, but has 
recently been converted into a solid at a temperature of —130.5°. 
It boils at 78.3°. It burns with a non-luminous flame, which 
does not leave a deposit of soot on substances placed in 
it. It is hence used for heating purposes. When mixed 
with air its vapor explodes when a flame is applied. Its 
effects upon the human system are well known. It intoxi- 
cates when taken in dilute form, while in concentrated form it 
is poisonous. When taken internally in large doses, it lowers 
the temperature of the body from 0.5° to 2°, although the sen- 
sation of warmth is experienced. 

Alcohol is the principal solvent for substances of organic 
origin. It is hence extensively used in the arts, as in the manu- 
facture of varnishes, perfumes, and tinctures of drugs. 

The many beverages which are in use depend for their effi- 
ciency upon the presence of alcohol in greater or smaller quantity. 
The milder forms of beer contain from 2 to 3 per cent ; light 
wines, such as claret, about 8 per cent ; while whiskey, brand} T , 
rum, and other distilled liquors sometimes contain as much as 60 
to 75 per cent. These distilled liquors are nothing but ordinary 
alcohol with water and small quantities of substances obtained 
from the fruit or grain used in their preparation, or obtained by 
standing in barrels made of oak wood. The different flavors 
are due to the small quantities of these substances. 



FERMENTATION. 41 

Chemical conduct of ethyl alcohol. All that was said in regard 
to the chemical conduct of methyl alcohol applies to ethyl 
alcohol. The action of acids, of phosphorus trichloride, of 
the alkali metals, and of oxidizing agents is the same as in the 
case of methyl alcohol, only the products formed contain the 
radical, ethyl, C 2 H 5 , instead of methyl. 

Note for Student. — The student is advised to write the equa- 
tions representing the action of hydrochloric, hydrobromic, and nitric 
acids ; of phosphorus trichloride ; and of potassium, upon ethyl alcohol. 
What is the composition of the acid formed by oxidation of ordinary 
alcohol? 

2. Ethers. 

As has been shown, when an alcohol is treated with potas- 
sium or sodium, compounds are formed having the for- 
mulas 

CH 3 ONa, CH3OK, C 2 H 5 OK, C 2 H 5 ONa. 

If one of these is treated with a mono-halogen derivative of 
a hydrocarbon, as, for example, iodo-methane, CH 3 I, reaction 
takes place thus : — 

CH 3 ONa + CH3I = C 2 H 6 + NaL 

These reactions leave very little room for doubt in regard to 
the structure of the compound C a H»jO. It must be represented 

by the formula CH 3 - O - CII 3 , or ?? 8 >0, or (0II,),,O. 

CH 8 

Comparing it with methyl alcohol, we see that it is obtained 

from the alcohol by replacing the hydrogen of the hydroxy] by 

methyl, CH 8 . Just as the alcohol is analogous to the hydroxide 

KOII, so the new compound is analogous to the oxide K.O. 

R is the representative of a class of bodies known as ethers. 

which are analogous to the oxides o\' the metals. Our ordinary 

ether is the chief representative of the class. 

While the reaction above mentioned serves admirably to show 

the relations between the alcohols and ethers, it is not the one 



42 DERIVATIVES OF METHANE AND ETHANE. 

that is made use of in their preparation. This consists in 
treating the alcohols with sulphuric acid, and distilling. 

Ethyl ether, C4H10O = (C 2 H 5 )20. — This is the substance 
commonly known simply as ether, or sulphuric ether. The latter 
name was originally given to it because sulphuric acid is used 
in its manufacture, and plainly not because any sulphur is con- 
tained in it. Ether can be made from alcohol by making the 
sodium compound of alcohol, C 2 H 5 ONa, and heating this with 
brom- or iodo-ethane thus : — 

C 2 H 5 ONa + C 2 H 5 I = (C 2 H 5 ) 2 + Nal ; 

or by converting the alcohol into ethyl iodide and heating this 
with silver oxide : — 

2 C 2 H 5 I + Ag 2 = (C 2 H 5 ) 2 + 2 Agl. 

Practically, however, ether can be made much more readily, 
and it is made on the large scale by mixing sulphuric acid and 
alcohol in certain proportions, and then distilling the mixture 
as described below. Two distinct reactions are involved in this 
process. First, when alcohol and sulphuric acid are brought to- 
gether, half the hydrogen of the acid is replaced by ethyl, thus : — 

C 2 H 5 OH + 5; > S0 4 = C ^ 5 > S0 4 + H 2 0. 

xi xi 

The product formed is called ethyl-sulphuric acid. 

Experiment 9. Slowly pour 20 to 30 co concentrated sulphuric acid 
into about the same volume of alcohol of 80 to 90 per cent. Stir thoroughly, 
and dilute with a litre of water. In an evaporating dish add powdered 
barium carbonate until the liquid is neutral. Filter, and examine the clear 
filtrate for barium. Its presence shows that a soluble barium salt has 
been formed. This is barium ethyl-sulphate, Ba^HsSO^. 

When ethyl-sulphuric acid is heated with alcohol, ether is 
formed, and sulphuric acid is regenerated thus : — 

C 2 H 5 OH + C ^ 5 > S0 4 = ^ > + H 2 S0 4 . 

Jti ^2^5 

The ether thus formed distils over j and, if alcohol is admitted 



ETHYL ETHER. 



43 



to the sulphuric acid, ethyl-sulphuric acid will again be formed, 
and with excess of alcohol it will yield ether. The actual 
method of procedure is described in 

Experiment 10. Arrange an apparatus as shown in Fig. 6. As ether 
is very volatile and inflammable, it is important that the condenser be con- 
nected with the receiver by means of an adapter, and the receiver placed 
in a vessel containing ice ; or a towel may be wrapped around the neck 
of the receiver and the condensing tube. In the flask put a mixture 
of 200 B alcohol, and 360 s ordinary concentrated sulphuric acid. It is 
better to mix them in another vessel, and allow the 
mixture to stand for some time until it is thoroughly 




Fig. 6. 

cooled down ; and then to pour off from any deposited solid as com- 
pletely as possible. Now heat until the thermometer indicates the 
temperature 140°. At this point the mixture boils, and ether begins to 
pass over. As soon as this is noticed, open the stop-cock of the vessel 
.1, and let a slow stream of alcohol pass Into the distilling flask through 
the tube 13, which must reach beneath the surface of the mixture. 
Regulate this stream so that the temperature remains as near 140° as 
possible. In this way the operation can be kept up for a considerable 
time, the alcohol admitted to the tlask passing out as ether, ami being 
collected together with some alcohol in the receiver. After about a 
half litre to a litre of distillate has been collected, stop the operation. 
The mixture in the distilling tlask can be kept in a stoppered bottle 
and used again when Deeded. Tour the distillate into a glass-Stoppered 



44 DERIVATIVES OF METHANE AND ETHANE. 

cylinder, and add water. The ether will rise to the top, forming a 
distinct layer, and can be removed by means of a pipette or separating 
funnel. It should be shaken in this way a few times with water; then 
treated with a little calcium chloride ; and, after standing, poured off 
into a dry flask, and distilled on a water-bath. 

N.B. Never boil ether over a free flame; and, in working with it, 
always carefully avoid the neighborhood of flames. In boiling it on a 
vjater-bath, do not heat the water to boiling. 

Ether is a colorless, mobile liquid of a peculiar odor and 
taste. It boils at 34.9°. (Hence the necessity for the pre- 
cautions mentioned above.) Its specific gravity is 0.736 at 0°. 
(What evidence have you had that it is lighter than water?) 
It is very inflammable. 

Experiment 11. Put a few cubic centimetres of ether in a small 
evaporating dish, and apply a flame. 

When its vapor is mixed with air, the mixture is extremely 
explosive. Ether is somewhat soluble in water, and water is 
also somewhat, though less, soluble in ether ; so that when the 
two are shaken together the volume of the ether becomes 
smaller, even though every precaution is taken to avoid evapor- 
ation. Ether mixes with alcohol in all proportions. It is a 
good solvent for resins, fats, alkaloids, and many other classes 
of carbon compounds. 

It is an excellent anaesthetic, and is used extensively in this 
capacity. In consequence of its rapid evaporation, it is used 
to produce cold, as in the manufacture of ice. So, also, when 
brought against the skin in the form of spray, the cold produced 
is so great as to cause insensibility. 

Experiment 12. In a thin glass test-tube put 5 CC water. Introduce 
the tube into a small beaker containing some ether. Force air over the 
surface of the ether by means of a bellows. The water will be frozen. 

Chemical conduct of ether. If we were dependent upon the 
decompositions and general reactions of ether for our knowledge 
of its structure, we should be left in grave doubt as to the rela- 



MIXED ETHERS. 45 

tions existing between it and alcohol. Its decompositions are 
mostly deep-seated, and not easily explained. Fortunately, as 
we have seen, its synthesis from sodium ethylate, C 2 H 5 ONa, and 
iodo-ethane, C 2 H 5 I, leaves us in no doubt regarding its structure. 
The simplest decompositions are these : — 

Heated with acidified water to 150° in a sealed tube, it is 
converted into alcohol : — 

C 2 H 5 > o + H > o = 2 C 2 H 5 OH. 
C 2 H 5 H 

Treated with hydriodic acid at a low temperature, alcohol 
and iodo-ethane are formed : — 

C 2 H 5>0 + H C2H50H + C2 h 5L 

Mixed ethers. — Just as ordinary or ethyl alcohol yields 
ethyl ether, so methyl alcohol yields methyl ether, (CH 3 ) 2 0. 
By modifying the method, a mixed ether, methyl- ethyl ether, 

C II 

2 5 > O, can be obtained. This is formed by treating sodium 

V^jAg 

methylate with iodo-ethane, or by treating sodium ethylate with 
iodo-methane : — 

CH 3 ONa + C 2 H 5 I = C ^ 5 > O -f Nal ; 
CH 3 

C 2 H 5 ONa + CH 3 I = C ^ > O + NaT. 

It is formed also by distilling methyl alcohol with ethyl-sul- 
phuric acid, or ethyl alcohol with methyl-sulphuric acid: — 

C 5* >° + C "I! 5 > SO, = ^"" >0 + 1I.SO, ; 

Jll I 1 V- 1 Ijj 

C 2 H 5>0+ CH, >S() ( -;||> >0 -f- ll,SO ( . 
rl H ^1 1;, 

Methyl ether and methyl-ethyl ether are very similar to ordinary 

ether. 



46 DERIVATIVES OF METHANE AND ETHANE. 

3. Aldehydes. 

It has been stated above that when methyl and ethyl alcohols 
are oxidized, they are converted into acids having the formulas 
CH 2 2 and C 2 H 4 2 , respectively. By proper precautions, prod- 
ucts can be obtained intermediate between the alcohols and 
acids, and differing from them in composition in that they 
contain two atoms of hydrogen less than the corresponding 
alcohols. These products are called aldehydes, from alcohol 
dehydrogenatum, from the fact that they must be regarded as 
alcohols from which hydrogen has been abstracted. The rela- 
tions in composition between the hydrocarbons, alcohols, and 
aldehydes are shown by these formulas : — 



Irocarbons. 


Alcohols. 


Aldehydes 


CH 4 


CH 4 


CH 2 


C 2 H 6 


C 2 H 6 


C 2 H 4 


etc. 


etc. 


etc. 



Formic aldehyde, Formal, Methanal, CH2O. — This alde- 
hyde is made by passing the vapor of methyl alcohol together 
with air over a heated platinum or copper spiral. When cooled 
to a low temperature it forms a liquid that boils at —21°. It is 
manufactured on the large scale, and comes into the market in 
solution under the name of formalin. It is used in the manu- 
facture of some dyes and as a preservative and disinfectant. 
When its solution in water is evaporated, a solid substance 
having the same composition as formic aldehyde is obtained. 
This is no doubt a polymeric variety, and it may be represented 
by the formula (CH 2 0)h. It is called paraformaldehyde. 

In order to gain a clear insight into the nature of the alde- 
hydes, it will be best to study the best-known representative of 
the class, which is acetic aldehyde. 

Acetic aldehyde, Ethanal, C 2 H;0 — This aldehyde is 
formed whenever alcohol is brought in contact with an oxidizing 



ACETIC ALDEHYDE. 



47 



mixture; as, for example, potassium dichromate and dilute 
sulphuric acid. 

Experiment 13. Dissolve a little potassium dichromate in water, 
and add sulphuric acid. Now add a few cubic centimetres of alco- 
hol, and notice the odor which is that of aldehyde. Notice, also, 
the change of color of the solution, showing the reduction of the 
chromate. 

As aldehyde is a very volatile liquid, it is difficult to collect it. 
In preparing it, it is therefore best to pass it into some liquid 
which will absorb it, and then afterwards separate it by some 
appropriate method. A good method is that described below. 

Experiment 14. Arrange an apparatus as shown in Fig. 7. Put 
120s granulated potassium dichromate in the flask A, which must have 
a capacity of 1J to 2 litres. Make a mixture of 160s concentrated sul- 




Pig. 



phuric acid, 4808 water, and 120* alcohol. Cool the mixture down to 
the ordinary temperature, and then pour it slowly through the funnel- 
tube B into the flask, which should stand on a water-bath containing 



48 DERIVATIVES OF METHANE AND ETHANE. 

warm water. The cylinders C and D are about half filled with ordinary 
ether, each one containing about 200 cc ether, and placed in the large 
vessel F, which contains ice water. The condenser should be supplied 
with water of about 30° C. 

Usually, when the alcohol, water, and sulphuric acid are poured upon 
the dichromate, the action begins without application of heat. At times 
it takes place rapidly, so that the liquid should always be added slowly. 
The aldehyde which is thus formed, together with some alcohol and 
water vapor, passes into the condenser-tube, where the greater part of 
the alcohol and water is condensed and returned to the flask, while 
the aldehyde, being much more volatile, passes into the ether and is 
there absorbed. After the action is over, the distilling vessel and con- 
denser are removed, and, at E, connection is made with an apparatus 
furnishing dry ammonia gas. The gas is passed into the cold ethereal 
solution of aldehyde to the point of saturation. A beautifully crystal- 
lized compound of aldehyde and ammonia, known as aldehyde-ammonia, 
is deposited. The ether is poured off, and the crystals placed on filter- 
paper. They gradually undergo change in the air, becoming yellow, 
and acquiring a peculiar odor. If the crystals are placed in a flask and 
treated with dilute sulphuric acid, pure aldehyde passes over, and can 
be condensed by ice-cold water. 

In the process of purification of ordinary alcohol it is filtered 
through charcoal. It is thus partly oxidized to aldehyde ; and, 
when it is afterwards distilled, the first portions that pass 
over contain aldehyde, which was formerly obtained on the 
large scale by repeated distillation of these " first runnings." 

Aldehyde is a colorless liquid, boiling at 21°. It mixes with 
water and alcohol in all proportions. Its odor is marked and 
characteristic. 

From the chemical point of view, the most characteristic prop- 
erty of aldehyde is its power to unite directly with other sub- 
stances. It unites with ox} T gen to form acetic acid ; with 
iiydrogen to form alcohol ; with ammonia to form aldehyde- 
ammonia, C 2 H 4 O.NH 3 ; with hydrocyanic acid to form alde- 
hyde hydrocyanide, C 2 H 4 O.HCN ; with the acid sulphites of 
the alkalies forming compounds represented by the formulas 
C 2 H 4 O.HKS0 3 and CoH 4 O.HNaS0 3 ; and with other substances. 
Indeed, if left to itself, it readily changes into polymeric modi- 



METALDEHYDE. 49 

fications, uniting with itself to form more complex compounds, 
paraldehyde and metaldehyde. 

Paraldehyde, 6 H 12 O 3 . — This is formed by adding a few 
drops of concentrated sulphuric acid to aldehyde, which causes 
the liquid to become hot. On cooling to 0°, the paraldehyde 
solidifies in crystalline form. It melts at 10.5°. It dissolves 
in eight times its own volume of water, and boils at 1 24°. When 
distilled with dilute sulphuric acid, hydrochloric acid, etc., it is 
converted into aldehyde. The specific gravity of its vapor has 
been found to be 4.583. This leads to the molecular weight 
132.4, and consequently to the formula C 6 H 12 3 . It is called a 
polymeric modification of aldehyde. 

Metaldehyde, CeH^Os. — Metaldehyde is formed in much 
the same way as paraldehyde, only a low temperature (below 
0°) is most favorable to its formation. It crystallizes in needles, 
which are insoluble in water, and but slightly soluble in alcohol, 
chloroform, and ether in the cold, though more readily at a 
slightly elevated temperature. When heated to 120° in a sealed 
tube, it is converted into aldehyde. Determinations by the 
freezing-point method show that the molecular weight of 
freshly prepared metaldehyde is the same as that of paralde- 
hyde. On standing it is converted into paraldehyde and, 
probably, a substance of the formula (C 2 H 4 0) 4 . Distilled with 
dilute sulphuric acid, etc., metaldehyde is easily converted into 
aldehyde. 

In consequence of the tendency of aldehyde to unite with 
oxygen, it is a strong reducing agent. When added to an 
ammoniacal solution of silver nitrate, metallic silver is deposited 
on the walls of the vessel in the form oi' a brilliant mirror. 

Experiment 15. To a dilute solution of silver nitrate add a solu- 
tion of ammonia until the silver oxide which is at first precipitated 
is aearly, though not quite, dissolved ; filter, warm gently in a clean 
test-tube, ami add a few drops of a very dilute solution of aldehyde. 



50 DERIVATIVES OF METHANE AND ETHANE. 

A brilliant mirror of metallic silver will appear. This method is used 
in the manufacture of mirrors. What becomes of the aldehyde ? 



Chemical transformations of aldehyde. As aldehyde is pro- 
duced from alcohol by oxidation, so alcohol can be formed 
from aldehyde by reduction : — 

C 2 H 6 + O = C 2 H 4 -f H 2 ; 

C 2 H 4 -f H 2 = C 2 H 6 0. 

By oxidation aldehyde is converted into an acid of the formula 
C 2 H 4 2 , which is acetic acid ; and, by reduction, acetic acid is 
converted into aldelryde : — 

C 2 H 4 + O = C 2 H A ; 

C 2 H 4 2 + H 2 = C 2 H 4 + H 2 0. 

Treated with phosphorus pentachloride, aldehyde yields ethyl- 
idene chloride, C 2 H 4 C1 2 (which see) . This reaction is of special 
interest and importance, as it helps us to understand the relation 
between aldehyde and alcohol. Alcohol, as has been shown, 
is the hydroxide of ethyl, C 2 H 5 .OH. When oxidized it loses 
two atoms of hydrogen. Is the hydrogen of the hydroxyl 
one of the two which are given off? If so, what readjustment 
of the oxygen takes place? Such are the questions which we 
have a right to ask. 

To understand the action of phosphorus pentachloride on 
aldehyde, it will be necessary to consider briefly the action of 
this reagent in general upon compounds containing oxygen. 
When it is brought in contact with water, the first change is 
represented by the equation 

H 2 + PC1 5 = POCI3 + 2 HC1. 

Next, the oxi chloride, POCl 3 . is acted upon thus : — 

3 H 2 + POCI3 = PO(OH) 3 -f 3 HC1. 

Or, expressing both changes in one equation, we have : — 

4 H 2 + PC1 5 = PO(OH) 3 + 5 HC1. 



ALDEHYDE. 51 

The phosphorus pentachloride gives up its chlorine and takes 
up oxygen, or oxygen and hydrogen, in its place. This is the 
general tendency of the chlorides of phosphorus. 

Now, when a chloride of phosphorus is brought together with 
an alcohol, chlorine is substituted for the oxygen, two atoms of 
the latter for one of the former, thus : — 

C 2 H 5 .OH + PC1 5 = C 2 H 5 ChClH + POCl 3 . 

But as hydroxyl, — — H, is univalent, its place cannot be 
taken by two atoms of chlorine and one of hydrogen, and the 
two chlorine atoms have not the power of linking the hydrogen 
to the ethyl. Hydrochloric acid is given off, and a compound is 
formed, which may be regarded as alcohol in which one chlorine 
atom takes the place of the hydroxyl. This is the kind of 
action that takes place whenever a chloride of phosphorus acts 
upon a compound containing hydroxyl ; and hence the reaction 
is made use of for determining whether hydroxyl is or is not pres- 
ent in a compound. 

When aldehyde is treated with phosphorus pentachloride, 
the action is entirely different from that just described. Instead 
of one chlorine atom taking the place of a hydrogen and an 
oxygen atom, two chlorine atoms take the place of the oxygen 
atom : — 

C 2 H 4 + PC1 5 = CoH 4 CL> + POCl 3 . 

If the explanation above offered of the action of phosphorus 
pentachloride on alcohol is correct, it follows that aldehyde is 
not a hydroxyl compound. We can readily understand why t wo 
chlorine atoms should take the place of the oxygen atom, if the 
latter is in combination only with carbon as in carbon monoxide, 
CO. There is an essential difference between this kind of com- 
bination and that which we have in hydroxy] asC— 0— H, In 
the latter condition the oxygen serves to conned carbon with 
hydrogen; in the former it is in combination only with the 
carbon, and, presumably, the force which holds it can also hold 
two atoms oi' chlorine Or Of 8»n"y other univalent element with 



52 DERIVATIVES OF METHANE AND ETHANE. 

which it can unite. So that, if oxygen is in a compound in 
the carbon monoxide condition, we should expect two chlorine 
atoms to take its place when the compound is treated with 
phosphorus pentachloride. Let R.CO represent any such com- 
pound ; then we should have : — 

RCO + PC1 5 = R.CC1 2 + POCl 3 ; 

while, when oxygen is present in the hydroxyl condition, we 
have : — 

R.C - O - H -f PC1 5 = R.CC1 -f POCI3 + HC1. 

Just as the latter reaction is used to detect the presence of 
hydroxyl oxygen, so the former is used to detect oxygen in the 
other condition, which is commonly known as the carbonyl con- 
dition. 

In terms of the valence hypothesis, it is said that in the 
hydroxyl compounds oxygen is in combination with carbon with 
one of its affinities, and with hydrogen with the other, while in 
the carbonyl compounds it is in combination with carbon with 
both its affinities as represented thus, C= O. 

According to the above reasoning aldehyde is a carbonyl 
compound, or it contains the group CO. The simplest alde- 
hyde must therefore be represented by the formula H 2 C = O. 


II 
Its homolcgue, acetic aldehyde, is CH 3 .C — H. The peculiar prop- 
erties of aldehyde are believed to be due to the presence of this 

li 
group, C — H, which is called the aldehyde group. We do not 

know that the double line in the formula conveys a correct idea 
in regard to the relation between the carbon and oxygen. All 
that we know is that these two elements do occur in two differ- 
ent relations to each other, and the formulas C — O — H and 
C — O recall these relations. They are expressions of facts 
established by experiment. Our notions in regard to these 
relations are largely dependent upon the reactions with the 
chlorides of phosphorus referred to above. 



CHLORAL. 53 

Chloral, trichloraldehyde, CCls.CHO. — When chlorine 
acts directly upon aldehyde, complicated reactions take place 
which need not be discussed here. If, however, water and 
calcium carbonate are present, substitution takes place, and 
trichloraldehyde is formed. When alcohol is treated with 
chlorine, a double action takes place : 1st. The alcohol is 
changed to aldehyde thus : — 

CH 3 .CH,OH + CI, = CH3.COH + 2 HC1. 

Then the chlorine acts upon the aldehyde, and is substituted 
for the three hydrogens of the methyl, forming trichloralde- 
hyde : — 

CH3.COH + 6 CI = CCl 3 .COH + 3 HC1. 

In reality the aldehyde first formed acts upon the alcohol, 
forming an intermediate product which is acted upon by the 
chlorine. The chlorine product thus formed breaks up, forming 
chloral. The essential features of the reaction, however, are 
stated in the above equations. Trichloraldehyde is the sub- 
stance commonly known as chloral. It is simply the tri-chlo- 
rine substitution product of aldehyde. It has all the general 

properties of aldehyde, and the conclusion is therefore justified 



II 
that it contains the aldehyde group - CH. 

Chloral is a colorless liquid, which boils at 97°, and has the 

specific gravity 1.54 at 0°. 

Note for Student. — Give the formulas o\' compounds formed when 
chloral is brought tog-ether with ammonia,' hydrocyanic arid, ami the 
acid sulphites of the alkalies. What, is the formula of the arid formed 
by its oxidation ? The answer is given in the statement that the general 
chemical conduct of chloral is the same as that oi aldehyde. 

When chloral and water are brought together, they unite to 
form a crystallized compound, chloral hydrate^ C0HCI3O -\ H ,0, 
which is easily soluble in water, and crystallizes from the solu- 
tion in beautiful, colorless, monoelinic prisms. It melts at 57° 



54 DERIVATIVES OF METHANE AND ETHANE. 

and boils at 97.5°. Taken internally in doses of from 1.5 to 5 g , 
it produces sleep. In larger doses it acts as an anaesthetic. 

When treated with an alkali, chloral and chloral hydrate 
break up, yielding chloroform and formic acid : — 

CCI3.COH + KOH = CHCI3 + KCH0 2 . 

Chloral. Chloroform. Potassium 

formate. 

This reaction, taken together with those which give chloral 
from alcohol, enables us to understand the reaction which is 
used in making chloroform and iodoform. 

Note for Student. — How is chloroform made? How is the method 
explained? Answer the same questions for iodoform. The bleaching 
powder used in preparing chloroform furnishes chlorine. Is an alkali 

present? 

4. Acids. 

/When methyl and ethyl alcohols are oxidized, they are con- 
verted first into aldehydes, and then the aldehydes take up 
oxygen and are converted into acids. The relations in compo- 
sition between the hydrocarbons, alcohols, aldehydes, and acids 
are shown in the subjoined table : — 



Hydrocarbons. 


Alcohols. 


Aldehydes. 


Acids. 


CH 4 


CH 4 


CH 2 


CH 2 2 


C 2 H 6 


C 2 H 6 


C 2 H 4 


C 2 HA 


etc. 


etc. 


etc. 


etc. 



The two acids whose formulas are here given are the well- 
known substances, formic and acetic acids. 

Formic acid, Methanic acid, CH2O2. — This acid occurs 
in nature in red ants, in stinging nettles, in the shoots of some 
of the varieties of pine, and elsewhere. 

It can be prepared by distilling red ants, but is best pre- 
pared by heating oxalic acid with glycerol. Oxalic acid has the 



FORMIC ACID. 55 

composition represented by the formula C 2 H 2 4 . When heated 
in glycerol, the effect is to break it up into carbon dioxide and 
formic acid : — 

C 2 H 2 Q, = C0 2 + CH 2 2 . 

The formic acid distils over, and can be condensed. 

Experiment 16. Into a flask of 500 to 600 cc capacity put 200 to 
300 cc anhydrous, glycerol, and then add 30 to 40s crystallized oxalic 
acid. Connect the flask with a condenser, and insert a thermometer 
through the cork so that the bulb is below the surface of the glycerol. 
Heat gently. At 75° to 90°, carbon dioxide is evolved. Raise the tem- 
perature gradually to 112°-115°. When formic acid no longer distils 
over, add another portion of oxalic acid, and heat again. This opera- 
tion may be repeated a number of times without renewing the glycerol ; 
but, when about 100s of oxalic acid has been decomposed, enough 
formic acid for the purpose will have been formed, and collected in 
the receiver. Dilute the distillate to about half a litre, and, while 
gently warming it in an evaporating dish, add freshly precipitated and 
washed copper oxide in small quantities until no more is dissolved. 
Then filter, and evaporate the solution to crystallization. The beauti- 
fully crystallized salt thus obtained is copper formate. 

The formation of formic acid by oxidation of methyl alcohol, 
and by treatment of chloral with an alkali, has already been 
mentioned. The following methods are of special interest : — 

(1) By the action of carbon monoxide upon potassium hy- 
>droxide : — 

CO + KOH = H.CO.K. 

This method can be used for the preparation of formic acid on 
the large scale. Soda-lime acts as well as potassium hydroxide. 

(2) By the action of metallic potassium upon moist carbon 
dioxide (carbonic acid) : — 

2CO„ + K., + U..O = HCOjK + HCO3K, 
or 2CO s H, + K s = HCOjK + HCO s K + 1LO. 



56 DERIVATIVES OF METHANE AND ETHANE. 

(3) By treatment of a solution of ammoninm carbonate with 
sodium amalgam : — 

C0 3 (NH 4 ) 2 + 2 H = HC0 2 (NH 4 ) + H 2 + NH 3 , 
and HC0 2 (NH 4 ) + NaOH = HC0 2 Na + NH 3 + H 2 0. 

According to these last two methods formic acid appears as a 
reduction product of carbonic acid formed by the abstraction of 
one atom of oxygen : — 

H 2 C0 3 = H 2 C0 2 + 0. 

It is extremely important to bear this fact in mind, as it is of 
great assistance in enabling us to understand the relation exist- 
ing between the two acids, and between them and all other acids 
of carbon. It will be shown that all the acids of carbon may 
be regarded as derivatives of either formic acid or carbonic 
acid. 

(4) When hydrocyanic acid is treated with an acid or an 
alkali, it breaks up, forming ammonia and formic acid. The 
reaction may be represented thus : — 

HCN + 2 H 2 = H 2 C0 2 + NH 3 . 

Of course, if an acid is present, the ammonium salt of the acid is 
formed ; and, if an alkali is present, the formate of this alkali 
is formed. A reaction similar to this is used very extensively in 
the preparation of the acids of the carbon,, as will be shown. 

Anhydrous formic acid can be made by dehydrating either 
the copper or lead salt, and passing dry hydrogen sulphide over 
the salt placed in a heated tube. The acid distils over, and can 
be obtained perfectly pure by placing a little of the anhydrous 
salt in it and redistilling 

It is a colorless liquid which boils at 100.6° at 760 mm . 
It has a penetrating odor. Dropped on the skin, it causes 
extreme pain and produces blisters. Its specific gravity at 0° 
is 1.22. When cooled down it solidifies to a mass of crystals 
which melt at 8.6°. 



ACETIC ACID. 5T 

Concentrated sulphuric acid decomposes it into carbon mon- 
oxide and water : — 

H 2 CO, = CO + H 2 0. 

It is easily oxidized to carbonic acid. Hence it acts as a 
reducing agent. Heated with the oxides of mercury or silver, 
they are reduced to the metallic condition : — 

HgO + H 2 C0 2 = Hg + H 2 -f C0 2 . 

Like other acids, formic acid yields a large number of salts with 
bases, and ethereal salts or compound ethers with the alcohols. 
These derivatives may not be treated of here. The salts are 
all soluble in water, and some of them, as the lead, copper, and 
barium salts, crystallize very well. Some of the compound 
ethers will be mentioned when these substances are considered 
as a class. 

Acetic acid, Ethanic acid, C2H4O2. — The two methods 
by which acetic acid is exclusively made are, — 

(1) By the oxidation of alcohol ; and 

(2) By the distillation of wood. 

When pure alcohol is exposed to the air it undergoes no 
change. If, however, some platinum black is placed in it, 
oxidation takes place and acetic acid is formed. So also if 
fermented liquors which contain nitrogenous substances are 
exposed to the air, oxidation takes place, and the liquor becomes 
sour in consequence of the formation of acetic acid. A meat 
deal of acetic acid is made by exposing poor wine to the action 
of the air. The product is known as wine vinegar. The for- 
niation of vinegar has been shown to be due to the presence o( 
a microscopic organism (Mycoderma aceti) commonly known as 
lc mother-of -vinegar." This serves in some way to convey the 
oxygen from the air to the alcohol. The u quick- vinegar 
process," much used in the manufacture o[' vinegar, consists in 
allowing weak spirits o( wine to pass slowly through barrels 



58 DERIVATIVES OF METHANE AND ETHANE. 

filled with beech shavings which have become covered with 
Mycoderma aceti. The presence of the organism is secured by 
first pouring strong vinegar into the barrels, and allowing it to 
stand for one or two da}~s in contact with the shavings. 

When wood is distilled, a very complex mixture passes over, 
one of the constituents being acetic acid. By keeping the tem- 
perature down comparatively low, the amount of acetic acid 
obtained is increased. The distillate is neutralized with soda 
ash, and the solution of crude sodium acetate thus obtained 
evaporated to dryness. It is then treated with sulphuric acid, 
and distilled, when acetic acid passes over. 

Besides the two methods mentioned, there are two others 
which may be used for making acetic acid. One of them is a 
modification of a method referred to under formic acid, and, 
from the scientific point of view, both are of great interest. 
They are, — 

(1) By treating carbon dioxide with a compound known 
as sodium-methyl, which may be regarded as marsh gas, in 
which one hydrogen is replaced by sodium as shown in the 
formula CH 3 Na : — 

C0 2 + CH 3 Na = CH 3 .C0 2 Na. 

(2) By treating methyl cyanide, CH 3 CN, with an acid or an 

alkali : — 

CH 3 CN + 2 H 2 = CH 3 .C0 2 H + NH 3 . 

This reaction is analogous to that involved in the formation 
of formic acid from hydrocyanic acid (see p. 56). 

Whether the acid is made from alcohol or from wood, it must 
be purified. For this purpose it is passed through charcoal and 
distilled. It still contains water, from which it cannot be 
completely separated by distillation. When cooled down to a 
sufficiently low temperature it solidifies, and the water can 
then partly be poured off. By repeating the freezing, and 
distilling a few times, perfectly pure, anhydrous acetic acid 
can be obtained. 



ACETrC ACID. 59 

Experiment 17. Make pure acetic acid from the commercial sub- 
stance. First distil in fractions until a portion is obtained that boils 
between 110° and 119°. Put the vessel containing this in ice. The 
liquid will solidify almost completely. Pour off the little liquid which 
remains, and distil. 

Acetic acid is a clear, colorless liquid, which boils at 118°. 
It has a very penetrating, pleasant, acid odor, and a sharp acid 
taste. The piire substance acts upon the skin like formic acid, 
causing pain and raising blisters. It solidifies when cooled down, 
and the crystals melt at 16.7°. The pure acid which is solid at 
temperatures below 16° is known as glacial acetic acid. Its spe- 
cific gravity is 1.08 at 0°. It mixes with water in all proportions. 

Acetic acid is extensively used, chiefly in the dilute, impure 
form known as vinegar. Formic acid would answer perhaps as 
well. It is used in calico printing in the form of iron and alu- 
minium salts. With iron it gives hydrogen, which is needed in 
the manufacture of certain compounds used in making dyes, as, 
for example, aniline. It is an excellent solvent for many 
organic substances, and is therefore frequently used in sci- 
entific researches. 

Derivatives of acetic acid. Acetic acid yields a very large 
number of derivatives. They may be considered briefly under 
two heads : (1) Those which are formed in consequence of the 
acid properties and which necessitate a loss of the acid proper- 
ties, as the salts, ethereal salts, etc. ; and (2) those in which 
the acid properties remain essentially unchanged. 

Salts of acetic acid. The acetates of the alkalies wore the 
first compounds of carbon ever prepared. The potassium and 
sodium salts are used in the chemical laboratory. Both crystal- 
lize, the sodium salt particularly well and easily. 

Lead acetate, (OoII ;; Oo).jPb. This salt, which is commonly 
known as sugar of lead, is made on the large scale by dissolv- 
ing lead oxide in acetic acid. It crystallizes well, and is solu- 
ble in 1.5 parts of water at ordinary temperatures. Commer- 
cial sugar of lead frequently contains an excess of load oxide In 



60 DERIVATIVES OF METHANE AND ETHANE. 

the form of basic salts. A solution of such a mixture becomes 
turbid when allowed to stand in the air, or gives a precipitate 
when dissolved in ordinaiy spring water, in consequence of the 
formation of lead carbonate. 

Copper acetate, (C 2 H 3 2 )2Cu. This salt can be made by 
dissolving copper hydroxide or carbonate in acetic acid. It 
crystallizes in dark-blue, transparent prisms. A basic acetate, 
formed by the action of acetic acid on copper in the air, is 
known as verdigris. 

Copper aceto-arsenite, 3 CuAs 2 4 + (C 2 H 3 2 ) 2 Cu. This double 
salt is formed by boiling verdigris and arsenic trioxide together 
in water. It has a fine bright-green color, and is used as a 
pigment and as an insecticide. It is the chief constituent of 
emerald green, Paris green, or Schweinfurt's green. 

Iron forms two distinct salts with acetic acid, the ferrous 
salt, (C 2 H 3 2 ) 2 Fe + 4 H 2 0, and the ferric salt, (C 2 H 3 2 ) 6 Fe 2 . 
The latter is formed when sodium acetate is added to an acidi- 
fied solution of a ferric salt. At first the solution becomes 
deep-red in color ; but, on boiling, all the iron is precipitated 
as hydroxide. Hence this salt is used for the purpose of sepa- 
rating iron from manganese in analytical operations. 

Experiment 18. To a dilute solution of ferric chloride, contained 
in a small flask, add a little acetic acid and a solution of sodium 
acetate. Boil the red solution, and ferric hydroxide is precipitated, 
leaving the solution colorless. Filter, and examine the filtrate for iron. 

The ethereal salts will be mentioned briefly when this class 
of compounds is considered. The principal one is ethyl acetate 
or acetic ether, which is formed from acetic acid and ordinary 
alcohol. When a mixture of these two substances is treated 
with sulphuric acid, the ether is formed and can be recognized 
by its pleasant odor. This fact is taken advantage of for the 
detection of acetic acid. 

Experiment 19. To a mixture of about equal parts of acetic acid 
and alcohol, in a test-tube, add a little concentrated sulphuric acid, heat, 
and notice the odor. It is that of ethyl acetate or acetic ether. 



ACETYL CHLORIDE, ETC. 61 

Acetic anhydride or acetyl oxide, C 4 H 6 3 . — This sub- 
stance, which bears to acetic acid the relation of an anhydride, 
is made by abstracting water from the acid : — 

2 C 2 H 4 2 = C 4 H 6 3 + H 2 0. 

Like other acids, acetic acid contains hydroxyl, as will be 
shown below. We may hence represent the acid thus : 
C 2 H 3 O.OH. The part C 2 H s O is known as acetyl. Now when 
water is abstracted from the acid, the change takes place as rep- 
resented in this equation : — 



C 2 H 3 O.OH I = C 2 H s O 
C 2 H 3 O.OH j ' C 



H 3 0| 
H 3 Oi 



+ H 2 0. 



Hence, according to this, acetic anhydride appears as the oxide 
of acetyl, while the acid itself is the hydroxide. 

Acetic anhydride is a colorless liquid which boils at 138°. 
With water it gives acetic acido 

Acetyl chloride, Q&OCl.S Just as alcohol, when 
Acetyl bromide, C 2 H 3 OBr. j- treated with phosphorus tri- 
Acetyl iodide, 2 H 3 OI. J chloride, yields a chloride of 
ethyl, so acetic acid, when treated with the same reagent, yields 
acetyl chloride. The character of the reaction is the same in 
both cases. It consists in the replacement of hydroxyl by 
chlorine : — 

3 C 2 H 3 O.Oll\ PC1 3 = 3 C 2 H 3 0C1 -f P(OH) 3 . 

Acetyl chloride. 

Experiment 20. Arrange a dry distilling flask, with condenser and 

dry receiver, under a hood or out of doors. Brings together 9 parts 
(say 180«) strong acetic acid and G parts (say HW phosphorus tri 
chloride. Slightly heat the mixture on the water-bath, when acetyl 
chloride will distil over. Collect In a dry bottle. 

Acetyl chloride is a colorless liquid \x\\'w\\ boils at 55°, 
Water acts upon it very readily, acetic and hydrochloric acids 
being formed : — 

(UI,0(l + U.O = CaHaO.OH -f 111 I. 



62 DERIVATIVES OF METHANE AND ETHANE. 

In this case the chlorine is replaced by hydroxyl. As the sub- 
stance is volatile, it fumes in contact with the air in consequence 
of the formation of hydrochloric acid. It must be kept in 
tightly-stoppered bottles. In handling it, care must be taken 
not to bring it near the nose, as its odor is very suffocating, and 
it attacks the mucous membranes of the eyes and nose, produc- 
ing coughing and other bad results. 

Acetyl chloride is a valuable reagent much used in the exam- 
ination of compounds of carbon. Its value depends upon its 
action towards alcohols. When it is brought together with an 
alcohol, as, for example, methyl alcohol, hydrochloric acid is 
evolved, and the acetyl group takes the place of the hydrogen 
of the alcoholic hydroxyl : — 

CH3.OH + C 2 H 3 0C1 = CH 3 .O.C 2 H 3 + HC1. 

The product is an ethereal salt, methyl acetate. This kind of 
action takes place whenever an alcohol is treated with acetyl 
chloride. Hence if. on treating a substance with acetyl chloride, 
its composition is changed, showing that hydrogen is replaced by 
acetyl, we are justified in concluding that the substance contains 
alcoholic hydroxj'l. The bromide and iodide resemble the 
chloride very closely. 

Experiment 21. Treat a few cubic centimetres of absolute alcohol 
with acetyl chloride. Notice the evolution of hydrochloric acid and 
the odor of ethyl acetate. 

Substitution-products of acetic acid. These bear the same 
relation to acetic acid that the substitution-products of marsh 
gas bear to marsh gas. They are formed by the simple sub- 
stitution of a halogen, etc., for hydrogen. Only three of the 
four hydrogen atoms of acetic acid are capable of direct 
replacement. The fourth is the one to which the acid prop- 
erties are due. Hence the substitution-products are acid. The 
best known of these products are the chlor-acetic acids which 
are made by treating the acid with chlorine. They are 



RELATIONS BETWEEN COMPOUNDS OF CAHBON. 63 

mono - chlor - acetic, di-chlor- acetic, and tri - chlor - acetic acids. 
Their formation is represented by the following equations : — 

C 2 H 3 O.OH + Cl 2 = C 2 H 2 C10.0H + HC1 ; 
C 2 H 2 C10.0H + Cl 2 = C 2 HCl 2 O.OH + HC1; 
C 2 HCl 2 O.OH + Cl 2 = C 2 Cl 3 O.OH + HC1. 

When treated with nascent hydrogen they are converted 
back into acetic acid. They yield salts, ethereal salts, anhy- 
drides, etc., just the same as acetic acid itself. 

Theory in regard to the relations between the acids, alcohols, 
aldehydes, and hydrocarbons. The reactions and methods of 
formation of acetic acid enable us to form a clear conception in 
regard to the relation of its constituents. In the first place 
the presence of hydroxyl is shown by the reaction with phos- 
phorus trichloride. We hence have C 2 H 3 O.OH as the formula 
representing this idea. But several questions still remain to be 
answered. There is another oxygen atom to be accounted for ; 
and the relations between the hydroxyl and this oxygen must 
be determined if possible. The fact that this second oxygen 
is not readily replaced by chlorine indicates that it is not 
present as hydroxyl, and all methods of testing for hydroxyl 
fail to show its presence in acetyl chloride. Hence we may 
conclude that the second oxygen atom is present as carbonyl 

O 
II 
CO. This leads us to the formula II — C — O — H for the simplest 

acid, or formic acid. Accordingly, formic acid appears as 

carbonic acid, which is commonly represented by the formula 

O — C { i in which one hydroxyl has been reduced to hydrogen. 
x OII 

Wo have already soon that this reduction can bo accomplished 
without difficulty. Many other arguments might bo brought 
forward in favor of the viow that the above formulas express 
the relations between formic ami carbonic acids. Now, as 
acetic acid is the homologue oi' formic acid, wo have every 



64 DERIVATIVES OF METHANE AND ETHANE. 

reason to believe that it differs from the latter in that it con- 
tains methyl in place of the hydrogen, which is in direct com- 
bination with carbon, and this view is confirmed by the fact 
that acetic acid can be made from sodium methylate, CH 3 Na, 
and from methyl cyanide, CH 3 .CN. The acid must hence be 


" " OH 

represented by the formula CH 3 .C - OH or CO<q H 3 - The coni- 



II 
mon constituent of the two acids is the group C-O-H or -CO.OH, 

which is generally known as carboxyl. Acetic acid is closely 

related not only to formic but to carbonic acid. It may be 

OH 

regarded as carbonic acid, CO<q H , in which one hydroxyl is 

replaced by the radical methyl. In a similar way we shall see 
that all organic acids may be regarded as derived either from 
formic acid or from carbonic acid. Representing now the 
simplest hydrocarbon, alcohol, aldehyde, and acid, by the 
structural formulas deduced from the facts, we have 



f H 


rOH 
°1 H 


ci H 


C i H 


Ih 


Marsh gas 
(Methane). 


Methyl alcohol 
(Methanol). 





H C 



< OH. 

H LH 



Formic 

aldehyde 
(Methanal). 



Formic acid 
(Methanic acid) . 



Concerning the mechanism of the changes caused by oxida- 
tion, but little can be determined by experiment. We may 
regard methyl alcohol as the first and simplest product of 
oxidation of marsh gas. Starting with methyl alcohol, we 
might expect the next change to consist in the introduction 

r OH 
I f")XT 

of another oxygen atom, giving a body c -J R • But it has 

been found that, except under certain peculiar conditions, one 
carbon atom cannot hold two hydroxyls in combination, and 



RELATIONS BETWEEN COMPOUNDS OF CARBON. 65 

that, if such a compound is formed, it loses the elements of 

f OH 

I OH f° 
water, thus, C j H = C H + h 2 0. The result would be the 

iH I H 

aldehyde. This kind of change is illustrated in the formation 

of carbon dioxide from the salts of carbonic acid. Instead of 

OH 
getting the acid CO < „ , which we should naturally expect, we 

get this minus water : — 

CO<^E = C0 2 + H 2 0. 

Oxi 

Now, when the aldehyde is oxidized, another oxygen atom is 
introduced, and the substance thus produced is an acid, or the 
hydroxyl hydrogen can be replaced by metals, and has in general 
the characteristics of acid hydrogen. As soon as we have car- 
bon in combination with oxygen as carbonyl, and also with 
hydroxyl, the substance containing the combination is an acid. 

If, finally, the acid C ) OH is oxidized, it is probable that the 
(H 
same change takes place as when the alcohol is oxidized. That 

is to say, the hydrogen is probably replaced by hydroxyl, when 
a compound containing two hydroxyls in combination with one 
carbon atom would be the result. This would be ordinary car- 
bonic acid. But this breaks up into water and carbon dioxide, 
which, as we know, are the products of oxidation of formic 
acid. 

All the many representatives of the groat classes of carbon 
compounds known as the alcohols, aldehydes, and acids are 
closely related to the three fundamental substances, methyl 
alcohol, formic aldehyde, and formic acid. Replace one of 
the hydrogen atoms of methyl alcohol by a radical, and we get a 

f 0B 
new alcohol, which may be represented by the formula C \ -a ' 

I B 

So also a similar replacement o( a hydrogen atom in formic 



66 DERIVATIVES OF METHANE AND ETHANE. 

(0 

aldehyde gives another aldehyde, C^ H; and, finally, as we have 

IE 
seen, the acids of carbon may be represented by the formulas 

C ) OH or E.CO.OH. or CO < R , which show then relations to 

In oh' 

formic and carbonic acids. Hereafter, in writing the formulas 
of members of the three great classes, the structure will be repre- 
sented by writing the hydroxyl group OH, /the aldehyde group 
CHO, and the carboxyl group CO. OH or C0 2 H, separately 
from the rest of the formula. 



5. Ethereal Salts or Esters. 

Whenever an acid acts upon an alcohol, the acid is neutralized 
either wholly or partly, and a product analogous to the salts is 
formed. Thus nitric acid and ethyl alcohol give ethyl nitrate : — 

C 2 H 5 .OH + HN0 3 = C 2 H 5 .X0 3 4- H 2 0, 

just as nitric acid and potassium hydroxide give potassium 
nitrate. It has been pointed out that the radicals, methyl, CH 3 , 
and ethyl, C 2 H 5 , take the part of metals in the ethereal salts. 
We can thus get a series of methyl and ethyl salts with the 
various acids. 

As regards the preparation of these compounds, it should be 
remarked that the action between an alcohol and an acid does 
not take place as readily as that between an acid and a metallic 
hydroxide. Only a few of the strongest acids act directly 
without aid. Such, for example, are nitric and sulphuric acids, 
though even the latter is not completely neutralized by action 
upon alcohols, as has already been seen in the preparation of 

C H 

ethyl-sulphuric acid, 2 ° > S0 4 , for the purpose of making ether. 

Plainly ethyl-sulphuric acid is an acid ethereal salt, analogous 
to acid potassium sulphate. Both are still acid, though both 
are likewise salts. 



c.^^ c **>**«. 



ETHEREAL SALTS. 67 

The methods which may be used for preparing ethereal salts 
are the following : — 

(1) Treatment of an acid with an alcohol. This is capable 
of only very limited application, as in the case of a few of the 
strongest acids. 

(2) Treatment of the chloride of an acid with alcohol. This 
has been illustrated by the action of acetyl chloride, C 2 H 3 0.C1, 
upon methyl alcohol (see p. 62) : — 

C 2 H 3 0C1 + HO.CH3 = C 2 H 3 O.OCH 3 + HC1, 
or CH 3 .COC1 + HO.CII 3 = CH 3 ^COOCH 3 + HC1. 

(3) Treatment of the silver salt of an acid with a halogen 
substitution-product of a hydrocarbon. For example, ethyl 
acetate can be made by treating silver acetate with brom- 
ethane : — 

\CBj.COOAg + CsH^Br = CH 3 COOC 2 H 5 + AgBr. 

This reaction is well adapted to showing the relation between 
the salt and the ethereal salt, and leaves no room for doubt that 
the two are strictly analogous. 

(4) Treatment of a mixture of an alcohol and an acid with 
dry hydrochloric acid gas or strong sulphuric acid. The forma- 
tion of ethyl acetate b} T this method was illustrated in Experi- 
ment 19, p. 60. The sulphuric acid facilitates the action by 
uniting with the alcohol to form ethyl-sulphuric acid, which with 
the acid gives the ethereal salt : — 

C 2 H 5>S0 ^ + C H 3tC00 H = CII 3 .COOC 2 II, + I1 2 S0 4 . 

It is probable that the hydrochloric acid first acts upon the 
acid forming the chloride, and that this then acts upon the 
alcohol, forming the ethereal salt: — 

CH3.COOH + I1C1 = CH 8 .COCl + H a O ; 
CII3.COCI -f-C 2 H ft OH =CH s .COOC 8 H4+ HC1, 



68 DERIVATIVES OF METHANE AND ETHANE. 

Among the more important ethereal salts of methyl and ethyl 
alcohols, the following may be mentioned : — 

pTT 

Methyl-sulphuric acid, -p. 3 > S0 4 , formed by mixing 

methyl alcohol and sulphuric acid. The acid itself, as well as 
its salts, is very easily soluble in water. 

Ethyl nitrate, 2 H 5 NO 3 , formed by treating alcohol with 
nitric acid. Unless precautions are taken in mixing these 
reagents, complete decomposition of the alcohol will take place, 
and the action will be accompanied by a violent explosion. 

Bthyl-sulphuric acid, 2 fz° > S0 4 . Made in the same way 

as the methyl compound. The acid and its salts are easily sol- 
uble in water. When boiled with water it is decomposed, 
yielding alcohol and sulphuric acid : — 

C2 ^ 5 >S0 4 + H 2 = H 2 S0 4 + C 2 H 5 OH. 

Ethyl sulphate, (0 2 H 5 ) 2 SO 4 , is made by passing the vapor 
of sulphur trioxide into well-cooled ether : — 

(C 2 H 5 ) 2 + S0 3 = (C,H 5 ) 2 S0 4 . / 

Phosphoric acid yields ethyl phosphate, (C 2 H 5 ) 3 P0 4 , di-ethyl-phos- 
phoric acid, (C 2 H 5 ) 2 HP0 4 , and ethyl-phosphoric acid, C 2 H 5 H 2 P0 4 . 

There also are similar derivatives of arsenic, boric, silicic, and 
other mineral acids. 

Of the ethereal salts which the two alcohols form with formic 
and acetic acids, methyl and ethyl acetates are the best known. 
The methods of preparing them have already been given. 
The}' are both liquids having pleasant odors. This is indeed a 
characteristic of man} r of the volatile ethereal salts of the acids 
of carbon, and many of the odors of fruits and flowers are due 
to the presence of one or another of these compounds, Many 



SAPONIFICATION. 89 

of them also are used for flavoring purposes instead of the 
natural substances. 

Experiment 22. Make a mixture of 15 parts (150s) of ordinary 
concentrated sulphuric acid and 6 parts (60s) absolute alcohol. Add 
to it 10 parts (100s) sodium acetate. Distil from a flask. Redistil 
the distillate. The ethyl acetate thus formed boils at 77°. What 
reactions take place in this case? 

Decomposition of ethereal salts. Salts of most metals are 
decomposed when treated with an alkaline hydroxide, as caustic 
soda or caustic potash, the result being a salt of the alkali and 
the hydroxide of the replaced metal, as seen in the case of 
copper sulphate and sodium hydroxide : — 

CuS0 4 + 2NaOH = Cu(OH) 2 + Na 2 S0 4 . 

So also the ethereal salts are decomposed when treated with the 
alkalies, though, as a rule, not as readily as salts. It is usually 
necessary to boil the ethereal salt with the alkali when decom- 
position takes place, the radical, like the metal, appearing in 
the form of the hydroxide or alcohol, and the alkali metal taking 
its place. Thus, when ethyl sulphate is treated with a solution 
of caustic potash, this reaction takes place : — 

. (C 2 H 5 ) 2 S0 4 + 2 KOII = K 2 S0 4 + 2 C 2 H 5 .OH ; 

and when ethyl acetate is treated with caustic soda, we have this 
reaction : — 

CH 3 .COOC 2 H 5 + NaOH = CH 3 .COONa + C»H a OH. 

Experiment 23. In a 500 cc flask put 200 co water. 508 solid 

caustic potash, and 20 cc ethyl acetate. Connect with an inverted eon- 
denser, arranged as shown in Fig. 8. Boil gently for half an hour. 
Now connect, the condenser with the flask for distilling, and again boil. 
Examine the distillate for alcohol. Aeidit'y the contents of the flask 
with sulphuric aeid, and again distil. What passes over? 

All ethereal salts are decomposed by boiling with the caustic 
alkalies. As this decomposition is best known od the large scale 
in the preparation of soaps, it is commonly called saponification. 



70 



DERIVATIVES OF METHANE AND ETHANE. 



As will be shown, the fats are ethereal salts, and soap-making 
consists in decomposing these fats by means of the alkalies. 
Hence, generally, to' saponify an ethereal salt means to decom- 
pose it by means of an alkali into the corresponding alcohol and 
the alkali salt of the acid contained in it. 




Fig. 8. 



6. Ketones or Acetones. 

When an acetate is distilled, a liquid passes over which has 
the composition C 3 H e O, and a carbonate remains behind. The 
reaction has been carefully studied, and has been shown to take 
place in accordance with the following equation : — 



CHg.COO 
CH,.COO 



> Ca = C 3 H 6 + CaC0 3 . 



The substance C 3 H 6 is known as acetone. It is the best 
known representative of a class of compounds which are some- 
times called acetones, but more commonly "ketones. 

Acetone, Dimethylketone, Propanone, CsHeO. — This 
substance has long been known as a product of the distillation 
of acetates. It is contained in considerable quantities in the 



ACETONE. 71 

product obtained in the distillation of wood, and can be sepa- 
rated from the mixture after the removal of the acetic acid. 

It can be purified by shaking a mixture containing it with a 
concentrated solution of mono-sodium sulphite. It unites with 
the salt, forming a compound analogous to that formed with 
aldehyde. The double compound can be separated, and when 
distilled with the addition of potassium carbonate acetone passes 
over. 

Acetone is a colorless liquid having a penetrating pleasant 
ethereal odor. It boils at 56.3°. It is a good solvent for many 
carbon compounds, such as resins, fats, etc. 

On studying the conduct of acetone, it soon becomes evident 
that it more closely resembles the aldehydes than any other 
bodies thus far considered. It is plainly not an acid nor an 
alcohol. It acts entirely differently from either. It is not an 
ethereal salt, for on boiling with an alkali it does not yield an 
alcohol nor the salt of an acid. On the other hand, it unites 
with the acid sulphites like the aldehydes. Further, when 
treated with phosphorus pentachloride its oxygen is replaced by 
two chlorine atoms thus : — 

C 3 H 6 + PC1 5 = C 3 H 6 Cl 2 + POCl 3 ; 

and when treated with nascent hydrogen, it is converted into a 
substance having alcoholic properties. These facts lead to 
the conclusion that the substance contains carbouyl, CO, as the 
aldehydes do. This is shown in the formula CoII 6 CO. The 
formation from calcium acetate loads further to the belief that 
the group C 2 H 6 really consists of two methyls, as the simplest 
interpretation of the reaction is represented thus : — 

CH 3 COO>Ca = CIl3 >CO + CaCO a . 
CH3COO CHg X 

According to this, acetone is a compound o( fcwo methyl groups 
and carbouyl, or it is oarbon monoxide whose two available 
affinities have been satisfied by two methyl groups. 



72 DERIVATIVES OF METHANE AND ETHANE. 

We can test the correctness of this view by means of synthe- 
ses. If it is correct, it will be seen that acetone is closely 
related to acetyl chloride. It is acetyl chloride in which the 
chlorine has been replaced by methyl : — 

CH3.CO.Cl CH3.CO.CH3. 

Acetyl chloride. Acetone. 

Now, when acetyl chloride is treated with zinc methyl, Zn(CH 3 ) 2 , 
it yields acetone according to this equation : — 

2 CH 3 . C0C1 + Zn(CH 3 ) 2 = 2 CH 3 . CO . CH 3 + ZnCl 2 . 

The relation between acetone and ordinary acetic aldehyde 
is similar to that of an ethereal salt to its acid; that is, 
acetone is aldehyde, CH 3 .COH, in which the hydrogen has 
been replaced by methyl, CH 3 .CO.CH 3 . 

Like the aldehydes, the acetone has the power of taking 
up other substances, such as the acid sulphites, ammonia, 
hydrocyanic acid, hydrogen, etc. This power is in some 
way connected with the relation of the oxygen to the car- 
bon, which is the same in both compounds. Nevertheless, 
this condition of the oxygen does not always carry with it 
the same power as seen in the case of the acids which also 
contain carbonyl. 

By reduction with nascent hydrogen, acetone yields an _ alco- 
hol of the formula C 3 H 8 0, known as secondary propyl alcohol, 
which when oxidized yields acetone. In other words, the rela- 
tion between this alcohol and acetone is much the same as that 
between ethyl alcohol and acetic aldehyde. But while the alde- 
hyde by further oxidation yields acetic acid by simply taking 
up one atom of oxygen, acetone is decomposed by oxidizing 
agents, and yields acetic and carbonic acids. Towards oxidiz- 
ing agents, then, acetones (for it will be shown that other 
acetones conduct themselves in the same way) act entirely 
differently from the aldehydes. The alcohol above mentioned 



GENERAL STATEMENTS. 73 

as related to acetone is the simplest representative of a class of 
alcohols differing in some respects from the substances com- 
monly called alcohols. 



We have thus considered the most important representatives 
of six classes of oxygen derivatives of the hydrocarbons, and, 
by a study of their chemical conduct and the methods available 
for their preparation, have formed views in regard to the rela- 
tions between them. In our ordinary language we may express 
these relations briefly thus : The alcohols are the hydroxy 1 
derivatives of the hydrocarbons or the hydroxides of certain 
groups called radicals; the ethers are the oxides of these same 
radicals ; the aldehydes are compounds consisting of carbonyl, 
hydrogen, and a radical ; the acids are compounds of carbonyl, 
hydroxyl, and a radical, or, better, they are carbonic acid in 
which hydrogen and oxygen, or hydroxyl, have been replaced 
by a radical ; the ethereal salts are compounds like ordinary 
metallic salts, only they contain a radical in the place of the 
metal ; and, finally, the ketones are aldehydes in which the 
distinctively aldehyde hydrogen has been replaced by a radical, 
or they are compounds consisting of carbonyl and two radicals. 

These ideas are expressed in formulas thus, R being any 
univalent radical like methyl, CH 8 , or ethyl, C 2 H 5 : — 

Alcohol .... R-O-H. 
Ether R-O-R, 

Aldehyde. . . . R-C-1I. 

I! 

o 

Acid R-C-O-H. 

ii 

O 
Ethereal salt . . Ac— 0— R (Ac— O— H representing an\ 
monobasic acid). 

Ketone .... R-C-.K. 

II 




CHAPTER V. 

SULPHUR DERIVATIVES OP METHANE AND 
ETHANE. 

1. Mercaptans. 

The simplest derivatives of methane and ethane containing 
sulphur are the so-called mercaptans or sulphur alcohols. They 
can be made by a method similar to one described under the 
head of Alcohols. When a mono-halogen derivative of a hydro- 
carbon, as brom-methane, CH 3 Br, is treated with the hydroxide 
of a metal, as silver hydroxide, AgOH, an alcohol is formed : — 

CH 3 Br + AgOH = CH 3 OH + AgBr. 

So, also, when a similar halogen derivative is treated with a 
hydrosulphide instead of a hydroxide, a compound is obtained 
which may be regarded as an alcohol in which the oxygen has 
been replaced by sulphur : — 

CH 3 Br + KSH = CH 3 SH + KBr. 
The compound is called a mercaptan. 

Ethyl-mercaptan, C2H5.SH. — This substance can be pre- 
pared by treating iodo-e thane, C 2 H 5 I, with an alcoholic solu- 
tion of potassium hydrosulphide, KSH; also by distilling a 
mixture of the concentrated solutions of potassium ethylsul- 
phate and potassium hydrosulphide : — 

° 2 ^ 5 > S0 4 + KSH = K 2 S0 4 + C 2 H 5 SH. 

It is a liquid" of an extremely disagreeable odor; it boils at 37°; 
and is difficultly soluble in water. 

The name "mercaptan" was given to it on account of its 
action towards mercury. It readily forms a compound in which 
mercury takes the place of hydrogen, (C 2 H 5 S) 2 Hg ; and the 
name has reference to this power (mercurium captans). It 



ETHYL-MERC APT AN. 75 

forms many other well-characterized metallic derivatives like 
this mercury compound. 

When the sodium compound of mercaptan is exposed to the air, 
it takes up oxygen. So, also, when mercaptan itself is treated 
with nitric acid, it is oxidized, the product having the formula 
C 2 H 5 .S0 3 H. It will thus be seen that, though in composition mer- 
captan is analogous to alcohol, towards oxidizing agents it con- 
ducts itself quite differently. In the case of alcohol two atoms of 
hydrogen are replaced by one of oxygen. In the case of mercap- 
tan three atoms of oxygen are added directly to the molecule. It 
will be shown that this new acid, which is called etkyl-sulplionic 
acid, bears to sulphuric acid a relation similar to that which acetic 
acid bears to carbonic acid ; and that it bears to sulphurous acid 
a relation similar to that which acetic acid bears to formic acid. 

When treated with phosphorus pentachloride it yields a chlo- 
ride, C 2 H 5 . S0 2 C1 ; and, when this is treated with nascent hydro- 
gen (zinc and hydrochloric acid), it is reduced to mercaptan : — 

C 2 H 5 . S0 2 C1 + 6H = C 2 H 5 . SH + HC1 + 2 H 2 0. 

2. Sulphur Ethers. 

There are compounds known similar to the ethers, containing 
sulphur in the place of the oxygen of the ethers. Such are 
methyl sulphide, (CH 3 ) 2 S, and ethyl sulphide, (CaH 6 ) 8 S. These 
are made by treating brom- or iodo-methane or ethane with 

potassium sulphide : — 

2 C 2 H 5 I + K L ,S = (C 2 ] [ 5 ) 2 S + 2 KI ; 

or by treating the sodium salt of methyl or ethyl-mercaptan 
with methyl or ethyl iodide : — 

Cft.SNa + CaHJ = (C 2 H 8 ) 2 S + Nal, 

They are liquids with very disagreeable odors. When oxi- 
dized they are converted into sulphones, two atoms oi' oxygen 

being added, thus ( ;- ,,, -" , ^S | O a = :?f: 5 > SO* 



76 DERIVATIVES OF METHANE AND ETHANE. 

3. Sulphonic Acids. 

It was stated above, that when mercaptan is oxidized it is 
converted into an acid of the formula C 2 H 5 . S0 3 H, or ethyl-sul- 
phonic acid. This is the representative of a large class of sub- 
stances which are commonly made by treating carbon compounds 
with sulphuric acid. These sulphonic acids can best be studied 
in connection with another series of hydrocarbons. Under the 
head of Benzene (which see) it will be shown that, when this 
hydrocarbon is treated with sulphuric acid, a reaction takes 
place which may be represented thus : — 

C 6 H 6 + ™ > S0 2 = ^ > S0 2 + H 2 0. 

Benzene. Benzene-sulphonic acid. 

The sulphonic acid thus obtained can also be made by oxi- 
dizing the corresponding mercaptan or hydrosulphide, C 6 H 5 . SH. 
Accordingly, the sulphonic acid appears to be sulphuric acid in 
which a hydroxyl has been replaced by the radical C 6 H 5 . Sea- 
soning by analogy, which, fortunately, is supported by other 
arguments, we may conclude that ethyl-sulphonic acid formed 

from ethyl-mercaptan bears a similar relation to sulphuric acid, 

P IT 
and corresponds to the formula tja > S0 2 . So, also, methyl- 

sulphonic acid obtained by oxidation of methyl-mercaptan 

should be represented by the formula ttq 3 > S0 2 or CH 3 . S0 2 OH. 

Its relation to sulphuric acid is the same as that of acetic acid to 
carbonic acid. 

Another method by which the sulphonic acids can be pre- 
pared consists in treating a sulphite with a halogen substitu- 
tion-product. Thus ethyl-sulphonic acid can be prepared from 
potassium sulphite and iodo-ethane : — 

C 2 H 5 I + |>S0 3 = C ^>S0 3 + KI, 
or C 2 H 5 I + K J > S0 2 = °^ > S0 2 + KL 



SULPHONIC ACIDS. 77 

According to this reaction the sulphonic acids appear to be 
identical with the ethereal salts of sulphurous acid, but they 
do not conduct themselves like ethereal salts. The differ- 
ence is particularly noticeable in connection with the stability, 
the sulphonic acids as a class being much more stable than 
the ethereal salts as a class. At present it would be some- 
what premature to discuss fully the question as to their rela- 
tions. Whatever we may call them, they are closely related to 
sulphurous acid, and are derived from it by replacement of 
hydrogen by a radical, just as acetic acid may be regarded as 
derived from formic acid by replacement of hydrogen by a 
radical. These relations are represented by the following 
formulas : — 

Carbonic acid, CO < . Sulphuric acid, S0 2 < . 

OH OH 

H H 

Formic acid, CO < . Sulphurous acid, S0 2 < 

Acetic acid, CO < ^ 3 . Methyl-sulphonic acid, S0 2 < CH \ 

Any carbonic ) C0 R A ny sulphonic acid, SO a <* . 

acid, J OH J 2 OH 

The difference between a sulphonic acid and an ethereal salt of 
sulphuric acid should be specially noticed. Compare for this 

purpose ethyl-sulphuric acid, a J*>S0 2 , and ethyl-sulphonic 

C H 
acid, 2 5 > SO.,. Both are monobasic acids, and both contain 

ethyl, but there is a difference ol' one atom o( oxygen in their 
composition. The reactions of the substances are such as to 
lead to the conclusion that in ethyl-sulphonic acid the ethyl 
group is directly connected with the sulphur; and that in 
ethyl-sulphuric acid the connection is established by means o\' 
oxygen. The strongest argument in favor of this view is 
perhaps thai which is founded ^n the formation of the sulphonic 

acids by oxidation o\' the hydrosulphides or mercaptans. It 



78 DERIVATIVES OF METHANE AND ETHANE. 

can hardly be doubted that in ethyl-mercaptan the sulphur is in 
direct combination with the ethyl; or, to go still farther, that 
it is in combination with carbon as represented in the formula 

H 
H 3 C — C — S — H. Now, by oxidation of mercaptan, three atoms 

H 
of oxygen are added, and the simplest view we can take of the 
reaction is that the sulphur is left undisturbed in its relations to 
ethyl, but that it has taken up the oxygen, as represented in the 
formula C 2 H 5 — S0 2 .OH. As has been shown, the oxygen can 
be removed again by nascent hydrogen, and the result is mer- 
captan. The study of the sulphonic acids in their relations to 
sulphuric and sulphurous acids has been of considerable assist- 
ance in enabling chemists to form conceptions in regard to the 
relations of the constituents of the two latter. The view which 
is forced upon us by a consideration of the reactions described 
above is that sulphurous acid differs from sulphuric acid in 
containing a hydrogen atom in place of hydroxyl, as represented 

OTT TT 

in the formulas S0 2 < and S0 2 < ; and, further, that in 

sulphurous acid one hydrogen is in combination with sulphur 
and the other with oxygen. 



CHAPTER VI. 

NITROGEN DERIVATIVES OP METHANE AND 
ETHANE.' 

The simplest compounds of carbon containing nitrogen are 
cyanogen and hydrocyanic acid. Strictly speaking, neither can 
be regarded as a derivative of a hydrocarbon, unless indeed we 
consider hydrocyanic acid as marsh gas, in which three hydro- 

f H 

TT 

gen atoms have been replaced by one nitrogen : C J and 

(N H 

C < • That-, however, is a mere matter of words, as there is 
( H 

nothing in the conduct of either substance, or in the methods of 
formation of hydrocyanic acid, that would lead us to suspect 
any relation between them. Though cyanogen and hydrocyanic 
acid are therefore not to be considered as derivatives of the 
hydrocarbons, they form the starting-point for the preparation 
of so many important compounds that they and their simpler 
derivatives must receive some consideration at this stage. 

Cyanogen, (CN),. — All organic compounds that contain 
nitrogen give sodium cyanide when ignited with sodium. So. 
also, potassium cyanide is formed when charcoal containing 
nitrogen is heated with potassium carbonate. Cyanogen itself 
is most readily made by healing mercuric cyanide, Hg(CN) 2 . 
The decomposition that takes place is, in the main, like the 
simple decomposition of mercuric oxide in preparing oxygon : — 

Hg(CN) a = Ilg + (CN),j 
HffO - Hff + O. 



2 V d 7| 

80 DERIVATIVES OF METHANE AND ETHANE. 

But, in heating mercuric cyanide, a black solid substance, para- 
cyanogen, is formed, and remains behind in the retort. It has the 
same composition as cyanogen, and although its molecular weight 
is not known, it is presumably a polymeric form of cyanogen. 

Cyanogen (from kvolvos, blue) owes its name to the fact that 
several of its compounds have a blue color. It is a colorless 
gas, which is easily soluble in water and alcohol, and is extremely 
poisonous. It burns with a purple-colored flame. 

In aqueous solution, cyanogen soon undergoes change, and a 
brown amorphous body is deposited. In the solution are found 
hydrocyanic acid, oxalic acid, ammonia, carbon dioxide, and 
urea. A little dilute acid prevents this decomposition. 

The compounds containing the cyanogen group, GN, may be 
compared with those containing the halogens. In them the 
cyanogen group plays the same part as the halogen atom in the 
halides. Thus we have : — 

AgCl AgCN 

KC1 KCN 

FeCl 2 Fe(CN) 2 

etc. etc. 

Hydrocyanic acid, HON. — This acid, which is commonly 
called prussic acid, occurs in nature in amygdalin in combina- 
tion with other substances, in bitter almonds, the leaves of the 
cherry, laurel, etc. It is prepared by decomposing metallic cya- 
nides with hydrochloric acid, as represented in the equation : — 

KCN + HC1 = KC1 + HCK 

It can also be made by treating chloroform with ammonia : — 

CHCI3 + NH3 =HCN +3HC1, 
or CHCI3 + 5 NH 3 == M 4 . CN + 3 NH 4 C1. 

It is a volatile liquid, boiling at 26.5°, which solidifies at — 15°. 
It has a very characteristic odor, suggesting bitter almonds. It 
is extremely poisonous. It dissolves in water in all proportions, 
and it is this solution which is known as prussic acid. Pure 



POTASSIUM FERROCYANIDE. 81 

hydrocyanic acid may be kept unchanged. When water or 
ammonia is present, it decomposes and gives ammonia, formic 
acid, oxalic acid, and a brown substance. By boiling with 
alkalies or acids, it is converted into formic acid and ammonia 
(see p. 56). 

Hydrocyanic acid can be detected by the fact that when its 
solution is saturated with caustic potash, and a solution con- 
taining a ferrous and a ferric salt is added, a precipitate of 
Prussian blue is formed when the mixture is acidified ; or, by 
adding yellow ammonium sulphide to its solution, evaporating 
to dryness, and then adding a drop of a solution of ferric chlo- 
ride. If hydrocyanic acid was present, the solution turns a 
deep blood red in consequence of the formation of ferric sul- 
phocyanate. 

Cyanides. — Hydrocyanic, like hydrochloric acid, forms a 
series of salts, which are called the cyanides. The cyanides of 
the alkali metals and of mercury are soluble in water. The 
cyanides of the heavy metals have a marked tendency to form 
double cyanides, and those double cyanides which contain an 
alkali metal are soluble in water. Hence, the precipitates 
formed by potassium cyanide, in solutions containing the heavy 
metals, are dissolved by excess of the cyanide. 

Potassium cyanide, KCN. —When potassium ferrocya- 
nide is ignited, pure potassium cyanide is formed according to 
this equation : — 

K 4 Pe (CN) 6 = 4 KCN + FeC a + N ,. 

Plainly only two-thirds of the cyanogen is thus obtained in the 
form of the potassium salt. In order to obtain a larger yield 
of cyanide it has been customary to molt together potassium 
carbonate and ferrocyanide. The reaction that takes place is 
represented thus : — 

K 4 Fe (CN), + K 2 C0 8 - 5 KCN + KCNO + CO, + IV 
The product contains potassium oyanate. Potassium cyanide, 



82 DEBIT ATIVES OF METHANE AND ETHANE. 

free from the cyanate, but containing sodium cyanide, is now- 
made on the large scale by heating together dehydrated potas- 
sium f errocyanide and metallic sodium : — 

K 4 Fe (CN) 6 + 2 Na = 4 KCjST + 2 NaCN + Fe. 
Potassium cyanide is a violent poison. It is very easily soluble 
in water, but is easily decomposed by it, yielding ammonia and 
potassium carbonate. The solution has an alkaline reaction. 
It is decomposed by carbon dioxide and hence has the odor of 
hydrocyanic acid. It precipitates almost all metallic salts, the 
solution in excess forming double cyanides. 

Among the best-known double cyanides are the two salts, 
potassium f errocyanide and potassium ferricyanide. The former 
is commonly called yellow prussiate of potash, and the latter 
red prussiate of potash. 

Potassium ferrocyanide, 4 KCN.Pe(CN)2 + 3 H 2 0- — 
This salt is made on the large scale by melting together, in iron 
vessels, refuse animal substances {i.e., organic matter contain- 
ing nitrogen) with potassium carbonate and iron. The mass is 
treated with water, and the salt which is thus extracted puri- 
fied by crystallization. 

It crystallizes in large monoclinic tables, and is soluble in 
about four parts of water at 15°. 

Experiment 24. 1 Make a mixture of 8 parts (100&) dehydrated 
potassium ferrocyanide and 3 parts (60s) dry potassium carbonate. Fuse 
in an iron crucible, at a low red beat, until a specimen taken out and 
placed on a stone is white when solid. Then pour out on a flat, smooth 
stone, and afterwards break up and put in a dry bottle. 

When treated with dilute sulphuric acid, the ferrocyanide 
yields hydrocyanic acid thus : — 

2[4KCKFe(CN) 2 ] + 3H 2 S0 4 

= 6 HCN + 2[KCN.tfe(CN) 2 ] + 3 K 2 S0 4 . 
This reaction is the one actually made use of for the prepara- 
tion of hydrocyanic acid. 

1 Experiments 24 and 26 may be postponed until urea is studied, when they may be 
combined with the artificial preparation of urea. 



CYANIC ACID. 83 

Potassium ferrocyanide is the starting-point for the prepara- 
tion of all compounds containing cyanogen. 

Potassium ferricyanide, 3 KCN.Fe(CN)3. — This salt, 
known as red prussiate of potash, is prepared by oxidizing the 
ferrocyanide, either by means of chlorine or of potassium 
permanganate. 

Experiment 25. Dissolve 26s potassium ferrocyanide in 200 cc cold 
water, and add 8 CC ordinary concentrated hydrochloric acid. Into this 
pour slowly a cold solution of 2e of potassium permanganate in 300 cc water. 
The oxidation is complete when a drop added to ferric chloride gives a 
brownish-red color, but no precipitate. Neutralize with chalk, filter, and 
evaporate on a water-bath. 

Potassium ferricyanide is easily soluble in water, and crys- 
tallizes from its concentrated solutions in large, dark-red rhombic 
prisms. 

In alkaline solutions it is an excellent oxidizing agent. 
Eeducing agents, such as hydrogen sulphide, sodium thiosul- 
phate (hyposulphite), etc., convert it into the yellow salt. 

(1) Prussian blue, (2) TurnbuWs blue, and (3) soluble Prussian 
blue are complex cyanides of iron represented by the formulas 

(1) 4Fe(CN) 3 .3 Fe(CN) 2 or Fe 4 '''[Fe''(CN) 6 ] 3 iy , 

(2) 3Fe(CN) 2 .2Fe(CN) 3 or Fe 3 ''[Fe"'(CN) 6 ] 2 "', and 

(3) KCN.Fe(CN) 8 .Pe(CN) 3 or KFe"pV'(CN) 6 ] lT , respectively. 

For a full account of the many compounds of the metals and 
cyanogen, the student is referred to larger works. 

Cyanogen chlorides. — When chlorine is allowed to act 
upon cyanides or dilute hydrocyanic acid, a volatile liquid is 
formed which has the composition represented by the formula 
CNC1. It boils at 15.5°, and its vapor acts upon the eyes, 
causing tears. It is known as liquid cyanogen chloride todistin- 
guish it from solid cyanogen chloride. The latter lias the formula 
(CN) 3 C1 8 , and is formed by treating anhydrous hydrocyanic 
acid with chlorine in direct sunlight. The Liquid variety i>> 
partially transformed into the solid when kept in sealed tubes. 



84 DERIVATIVES OF METHANE AND ETHANE. 

Similar compounds of cyanogen with, bromine and iodine are 
known. 

Cyanic acid, NCOH. — When a cyanide of an alkali is 
treated with an oxidizing agent, it takes up oxygen and is con- 
verted into a cyanate : — 

NCK + = NCOK. 

Experiment 26. * Dehydrate slowly 125s potassium ferrocyanide in 
an iron pan on a gas stove ; powder the dried salt and heat gently 1 to 2 
hours. Fuse 75s potassium dichromate, cool, powder finely, and mix 
thoroughly with the ferrocyanide. Bring the warm mixture in small 
portions with an iron spoon into a shallow iron pan which is heated suf- 
ficiently to cause the powder to glow and turn black. Stir rapidly during 
the reaction. Powder the porous mass, bring it while still warm into a 
mixture of 450 cc of 80 per cent alcohol and 50 cc methyl alcohol in a litre 
balloon-flask and heat to boiling in a water-bath. The water in the bath 
should be boiling and the alcohol warm when the cyanide is made. Boil 
for five minutes ; allow the undissolved part to settle and pour the clear 
solution through a plaited filter into a beaker standing in ice-water. The 
potassium cyanide separates as a heavy white crystalline powder. Shak- 
ing the flask in ice-water hastens the crystallization. Let the salt settle. 
With the mother-liquor repeat three times without delay the extraction 
of the black mass, boiling ten minutes each time. Filter, with the aid 
of a pump, each portion as soon as obtained ; wash the united portions 
with ether ; and dry in a desiccator over sulphuric acid. The ferrocya- 
nide must be anhydrous and the work must be done rapidly. The hot 
alcoholic solution must be cooled rapidly to prevent decomposition of 
the cyanate. 

Cyanic acid is readily decomposed by water yielding ammo- 
nia and carbon dioxide : — 

NCOH + H 2 = NH 3 + C0 2 . 

The potassium salt is easily soluble in water, but is decom- 
posed by it, yielding ammonia and potassium carbonate : — 

NCOK + 2 H 2 = KHCOg + NH 3 . 

The most interesting salt of cyanic acid is ammonium cyanate, 
NCO . NH 4 . It can be made by adding ammonium sulphate to 

1 See Note, p. 82. 



STTLPHO-CYANIC ACID. 85 

a solution of the potassium salt. It is easily soluble in water ; 
but, if allowed to stand in solution, or if its solution is heated, 
it is completely transformed into urea, which is isomeric with it. 
The interest connected with this transformation was referred to 
in the introductory chapter (p. 1). It will be treated of more 
fully under urea. 

Cyanuric acid, CsNsHsOs- — This acid bears a relation to 
cyanic acid similar to that which solid cyanogen chloride, 
(CN) 3 C1 3 , bears to the liquid variety. It is made by treating 
the solid chloride with water, and also by heating urea. It is 
a crystallized substance. 

Sulpho-cyanic acid, NCSH. — Just as the cyanides of the 
alkalies take up oxygen and are converted into cyanates, so also 
they take up sulphur and are converted into sulpho-cyanates : — 

CNK + S = NCSK. 

Potassium 
sulpho-cyanate. 

Experiment 27. Mix 46s dehydrated potassium ferrocyanide with 
17s dehydrated potassium carbonate, 32s sulphur, and 2" powdered char- 
coal. Fuse the mixture in an iron pan on a gas stove until the mass has 
"become liquid, and a sample no longer precipitates Prussian blue when 
added to a solution of ferric chloride but turns the solution blood-red : — 

K 4 Fe(CN) 6 + K 2 C0 3 + 8 S = 6 KCNS + FeS 2 + CO a + 0. 

The oxidation of the sulphur is prevented by the charcoal. Tour the fused 
mass on an iron plate, break it up into a coarse powder, and bring it into 
a flask with 250 cc alcohol. Boil with a return condenser for 10 minutes, 
and finally filter the hot solution, which contains only sulphocyanate. On 
cooling, the salt crystallizes in long colorless prisms. Pour off the mother- 
liquor, and use it to extract the residue again for a second crystallization. 
Evaporation of the mother-liquor will yield a third crystallization. The 
dried crystals should be preserved in well-Stoppered bottles, as the salt is 
very hygroscopic. 

Potassium sulpho-cyanate crystallizes in long striated prisms 
without water of crystallization. It is deliquescent When 
dissolved in water the temperature sinks markedly. When LOO 



86 DERIVATIVES OF METHANE AND ETHANE. 

parts of water of 10.8° are mixed with 150 parts of the salt, the 
temperature sinks to — 23.7°. By evaporation of the solution, 
the salt can be recovered. 

Experiment 28. Dissolve some potassium sulpho-cyanate in water, 
and note the temperature before and after introducing the salt. 

Ammonium sulpho-cyanate, NCS.NH 4 . This salt is most 
easily prepared by treating carbon disulphide with concen- 
trated alcoholic ammonia : — 

CS 2 + 4 M 3 = CNS .NH 4 + (KE 4 ) 2 S. 

Experiment 29. Mix 240 cc strong aqueous ammonia, 240 cc alcohol, 
and 60s carbon disulphide. Allow the mixture to stand for one or more 
days. Then distil down to one-third of the original volume, and filter 
while still hot the solution left in the flask. On cooling, ammonium 
sulpho-cyanate will crystallize out. 

The salt crystallizes in plates. It melts at 160° (try it), 
and at this temperature is partly transformed into the isomeric 
substance sulpho-urea. (Analogy to transformation of ammo- 
nium cyanate.) 

Having thus considered some of the more important simpler 
cyanogen compounds, we may now return to the nitrogen deriv- 
atives of the hydrocarbons. For convenience, these may be 
divided into three classes : — 

(1) Tliose ivhich are related to cyanogen ; 

(2) Tliose which are related to ammonia ; 

(3) Those which are related to nitric acid. 

Cyanides. 

Methyl cyanide, CH3.CN. — This compound is formed by 
distilling a mixture of potassium methyl-sulphate and potas- 
sium cyanide : — 

C ^ 3 > S0 4 + KCN = K 2 S0 4 + CH3CK 

It is a liquid boiling at 82°. 



ETHYL CYANIDE. 87 

According to the method of preparation, it must be regarded 
as an ethereal salt of hydrocyanic acid, containing methyl in the 
place of the potassium of the potassium salt. 

Ethyl cyanide, C2H5.CN. — Formed like the methyl com- 
pound. Also by heating chlor-ethane with potassium cya- 
nide : — 

C 2 H 5 C1 + KCN = C 2 H 5 .CN + KC1. 

It is a liquid boiling at 98°. 

The two most characteristic reactions of these cyanides are 
(1) that which is effected by caustic alkalies, and (2) that 
effected by nascent hydrogen. 

When methyl cyanide is treated with caustic potash, it yields 
acetic acid and ammonia : — 

CH 3 . GN + H 2 + KOH = CH 3 . C0 2 K + NH 3 . 

This reaction is strictly analogous to that which takes place 
with hydrocyanic acid, yielding formic acid (see p. 56). In 
the same way ethyl cyanide yields an acid of the formula 
C 3 H 6 2 (or C 2 H 5 .C0 2 H). Thus, by making a cyanide, we have 
it in our power to make an acid containing the same number of 
carbon atoms. 

This reaction, therefore, makes it possible to pass from an 
alcohol to an acid containing one atom of carbon more than 
the alcohol contains. It has been of great service in the study 
of the compounds of carbon. 

Note for Student. — Show how, by starting with methyl alcohol. 
acetic acid may be made by passing through the cyanide. 

There are two ways in which the cyanogen group can be 
linked to methyl in methyl cyanide; viz., either by the carbon 
atom, as represented in the formula H 8 C — C — N, OT by the 
nitrogen atom, as represented thus, H 8 C — N — C. The ease 
with which the nitrogen is separated from the compound, leav- 
ing the two carbon atoms united, as shown in the reaction with 
caustic potash, naturally leads to the conclusion that the for- 



88 



DERIVATIVES OF METHANE AND ETHANE. 



mer view is the correct one. If it is correct, it would appear 
to follow that in potassium cyanide the potassium is in combi- 
nation with carbon as represented in the formula K — C — 1ST, 
and further that in hydrocyanic acid the hydrogen is in combi- 
nation with carbon, as shown thus, H — C — 1ST. 

In consequence of the close relation existing between the 
cyanides and the acids, the former are often called the nitriles 
of the acids. Thus methyl cyanide, which is converted into 
acetic acid by boiling with caustic potash, is called the nitrile 
of acetic acid, or aceto-nitrile. In the same way hydrocyanic 
acid itself may be regarded as the nitrile of formic acid, or 
formo-nitrile. 

When methyl cyanide is treated with nascent hydrogen, 
it is converted into a substance which closely resembles am- 
monia, known as ethyl-amine. It will be shown to bear to 

f C2Hs 
ammonia the relation indicated by the formula N-{ H ; i.e., it 

Ih 

is ammonia in which one hydrogen has been replaced by ethyl. 

The reaction may be represented by the equation : — 

r rc 2 H 5 

H 3 C - C - N + 4 H = H 3 C - H 2 C - M 2 or N \ H 

LH 

This transformation strengthens the conclusion already reached, 
that the two carbon atoms in methyl cyanide are directly united. 
If this were not the case, it is difficult to see how a compound 
containing ethyl in which the two carbon atoms are unquestion- 
ably united, could be formed so easily from it. 

Just as methyl cyanide yields ethyl-amine when treated with 
nascent hydrogen, so hydrocyanic acid yields methyl-amine 

rCH 3 
N i H : — 

IH 



H-C-N + 4 H = H 3 C-NH 2 



or N 



CH 3 

H 

H 



ETHYL ISOCYANIDE. 89 

The amines, or substituted ammonias, will be treated of more 
fully hereafter. 

ISOCYANIDES OR CARBAMINES. 

If, in making an ethereal salt of hydrocyanic acid from a salt, 
the silver salt is used, a compound is obtained having the same 
composition as the cyanide, but differing very markedly from 
it. The substance thus obtained is called an isocyanide or car- 
bamine. 

Ethyl isocyanide or ethyl carbamine, C2H5NC. — This 
compound is obtained when silver cyanide and iodo-ethane are 
heated together : — 

C 2 H 5 I + AgNC = C,H 5 NC + AgI. 

It is also formed when chloroform and ethyl-amine (see above) 
are brought together : — 

CHCI3 + N ] H = C 2 H 5 NC + 3 HC1. 

It is a liquid boiling at 78.1°. It is characterized by an ex- 
tremely disagreeable odor. The methyl compound obtained by 
the same method boils at 59.6°, but otherwise has properties 
almost identical with those of ethyl isocyanide. 

The reactions of these substances are quite different from 
those of the cyanides. They are decomposed only with great 
difficulty by the caustic alkalies ; but, when treated with dilute 
hydrochloric acid, they undergo an interesting change, which 
maybe represented by the following equation for the methyl 
compound : — 

CH 8 .Ne + 2 H 2 = CH 8 -NH a + 1I.C0.I1. 

Methyl amino. Formic add. 

This reaction indicates thai in the isooyanides the cyanogen 
group is united to the radical by means o\' nitrogen, as repre- 
sented by the formula H 3 C — N — C. Heme it is, in all prob- 
ability, thai, when they undergo decomposition the nitrogen 



90 DERIVATIVES OF METHANE AND ETHANE. 

remains in combination with the radical, while the carbon of the 
cyanogen group passes out of the compound. The conduct of 
ethyl isocyanide is represented by the equation : — 

C 2 H 5 .NC + 2 H 2 = C 2 H 5 -NH 2 + H.C0 2 H. 

The reactions of the cyanides and of the isocyanides, and 
the conclusions drawn from them, admirably illustrate the 
methods used in determining the structure of compounds of 
carbon; and they are specially valuable, as the connection 
between the facts and the conclusions, as expressed in the 
formulas, can be traced so clearly. 

The fact, that the silver salt of hydrocyanic acid yields iso- 
cyanides, while the potassium and other salts yield cyanides 
with the halogen derivatives of the hydrocarbons, leads to the 
suspicion that in silver cyanide the metal may be in combina- 
tion with nitrogen and not with carbon, while in the potas- 
sium salt it may be in combination with carbon as represented 
in the formulas, — 

K - C - N and C - N - Ag. 

On the other hand, silver cyanide is formed by adding silver 
nitrate to a solution of potassium cyanide, so that it is prob- 
able that the silver and the potassium salts have analogous 
structures. The formation of the nitrile from the potassium 
salt may be accounted for by assuming that the first action 
between the cyanide and the halogen compound is addition, 

thus: - C 2 H 5 I 

K-CeN + C 2 H 5 I = K - C = N. 

If the addition-product thus formed should break down with 
elimination of potassium iodide, the compound formed would 
have the radical in combination with carbon. 

A fact to be borne in mind in connection with the peculiar 
relations between the cyanides and the isocyanides is that it 
has been shown that some of the isocyanides are transformed 
into cyanides by heat. 



CYANATES AND ISOCYANATES. 91 

Experiment 30. The odor of the isocyanides, as has been stated, is 
extremely disagreeable, and in concentrated form it is almost unbearable. 
A vivid impression in regard to this property may be produced by the 
following experiment. In a test-tube bring together a little chloroform, 
aniline, and alcoholic potash. The reaction takes place at once. It is 
better to perform the experiment out-of-doors, and in such a place that 
the tube with its contents can be thrown away without molesting any 
one. The aniline used is a substituted ammonia analogous to methyl- 
amine, containing the radical CeH 5 in place of methyl. The isocyanide 
formed has the formula C6H5.NC. 

Cyanates and Isocyanates. 

There are two series of compounds bearing to cyanic acid 
much the same relation that the cyanides and isocyanides bear 
to hydrocyanic acid. 

In the cyanates, which seem to be formed by passing cyanogen 
chloride into alcoholates (CH 8 ONa+CNCl = CH 3 OCN+NaCl), 
the radical is probably united to the cyanogen by means of 
oxygen, as represented in the formula CH 3 — — CN. 

In the isocyanates (first called cyanates), on the other hand, 
the radical is believed to be united to the cyanogen by means of 
nitrogen, as represented thus, CH 3 — N — CO. The isocyanates 
are made by distilling potassium cyanate with the potassium 
salt of methyl- or ethyl-sulphuric acid. They can be made also 
by bringing together the iodides of radicals, as iodo-methane 
and silver cyanate. They are very volatile substances, which 
have penetrating and suffocating odors. 

One of the principal reactions of the cyanates is that which 
they undergo with caustic alkalies, hydrochloric acid, etc. They 
yield a cyanate and an alcohol. 

The isocyanates readily yield substituted ammonias, just as 
the isocyanides do : — 

C 2 H r> - N - CO + 11,0 = C,H,. Nil, + CO,; 
CH a -N -CO + 11,0 = CH a .Ml, + CO* 

The views held in regard to the structure of the cyanates and 
isocyanates are based upon these reactions, which, as will be 



92 DERIVATIVES OF METHANE AND ETHANE. 

observed, are similar to those more fully presented in discuss- 
ing the difference between the cyanides and isocyanides. 

The existence of two cyanic acids, and of two series of salts 
derived from them, seems possible. 

S ULPHO-C VAN ATES . 

The ethereal salts of sulphocyanic acid are easily made by 
distilling potassium sulpho-cyanate and the potassium sait of 
methyl- or ethyl-sulphuric acid : — 

C ?" 3 > S0 4 + KSCN = CH 3 SCN + K 2 S0 4 . 

The ethyl compound, which is very similar to the methyl com- 
pound, is a liquid boiling at 146°. 

When boiled with nitric acid, it is oxidized to ethyl-sulphonic 
acid. Now, it has been shown above (see p. 77), that in ethyl- 
sulphonic acid the ethyl in all probability is in combination with 
the sulphur. It hence follows that, in the sulphocyanates 
obtained from potassium sulphocyanate, the radical is also 
in combination with sulphur, as indicated in the formula, 
C 2 H 5 — S — CX. This view is supported by the fact that ethyl 
sulpho-cyanate readily yields ethyl mercaptan as a product of 
decomposition. 

The sulphocyanates are converted into iso-sulpho-cyanates or 
mustard-oils by heat. 

ISO-SULPHO-CYANATES OR MuSTARD-OlLS. 

A number of compounds isomeric with the sulpho-cyanates 
are known. The best-known member of the class is ordinary 
mustard-oil. Hence they have been called mustard-oils, and 
they are generally known by this name. The mustard-oils are 
made by means of a series of somewhat complicated reactions, 
which it is rather difficult to interpret without a comparison 
with some similar reactions that take place between simpler 
substances. 



C0 2 + 2 NH 3 = OC < 



ISO-STJLPHOCYANATES. 93 

When dry ammonia and dry carbon dioxide act upon each 
other, so-called anhydrous ammonium carbonate is formed. This 

is really the ammonium salt of carbamic acid, OC < 0H . Its 
formation is represented thus : — 

NH 2 

(MH 4 * 

Now, remembering that carbon disulphide is similar to carbon 
dioxide, and that ethyl-amine is similar to ammonia, we can 
readily understand the reaction which takes place when these 
two substances are brought together : — 

CS 2 + 2 NH 2 C 2 H 5 = SO < s(N j| 3 c 2H5) • 

The product formed is the ethyl-ammonium salt of the acid 

I^TTp IT 

SC < Sl 5 , which may be called ethyl-sulpho-carbamic acid. 

When the ethyl-ammonium salt is treated with silver nitrate, 

t, o^ NHC 2 H 5 . . . , 

the corresponding silver salt, SC <§ A „. , is precipitated. 

And finally, when this salt is distilled, it breaks up, yielding 
ethyl mustard-oil, silver sulphide, and hydrogen sulphide : — 

2 SC <?^ C ^* = 2 SC-NCyEI 6 +H 2 S+Ag 2 S. 
bAg 

Ethyl mustard-oil is an oily liquid which does not mix with 
water. It has a very penetrating odor, and acts upon the 
mucous membranes of the eyes and nose in the same way as 
ordinary oil of mustard. The properties of the two are so 
much alike that one could be substituted for the other. 

Some of the arguments have been stated which lead bo the 
view that in the sulpho-cyanates the radical is iu combination 
with sulphur. r rhc reactions o\' the mustard-oils lead just as 

clearly to the conclusion that in them the radical is iu com- 
bination with nitrogen. In the Rrs1 place, they are made from 
the amines. A i ;aiu, when healed with water or with hvdro- 



94 DERIVATIVES OF METHANE AND ETHANE. 

chloric acid, ethyl mustard-oil is decomposed, yielding ethyl- 
amine, carbon dioxide, and hydrogen sulphide : — 

SC-NC 2 H 5 +2 H 2 = C 2 H 5 .NH 2 +H 2 S+C0 2 . 

And further, nascent hydrogen converts it into ethyl-amine and 
formic thioaldehyde (i.e., formic aldehyde in which the oxygen 
has been replaced by sulphur) : — 

SC-NC 2 H 5 +4 H = C 2 H 5 .NH 2 +H 2 CS. 

Thus, as will be seen, the tendency of the sulpho-cyanates is to 
yield sulphides of the radicals like ethyl sulphide, (C 2 H 5 ) 2 S ; 
the tendency of the iso-sulpho-cyanates is to yield substituted 
ammonias, like ethyl-amine, NH 2 .C 2 H 5 . These facts point to 
the relations expressed in the formulas, R — S — CN for the 
sulpho-cyanates, and R— N — CS for the iso-sulpho-cyanates 
or mustard-oils. 

In reviewing now the compounds of the hydrocarbons which 
are related to the cyanogen, we see that there are two isomeric 
series of these, the names and general formulas of which are 
given below : — 

Cyanides, R — C —N .... Isocyanides or |p ^p 

Carbamines, ) 

Cyanates, R— — CN .... Isocyanates, R — N — 00. 

Sulpho-cyanates, R — S — CN . . Iso-sulpho-cyan- -\ 

ates or Mus- I R-N-CS. 
tard-oils. ) 

Note for Student. — Study these compounds until the exact con- 
nection between the formulas and the facts above stated is clearly 
seen. 

Substituted Ammonias. 

When brom-ethane or any similar substitution-product is 
treated with ammonia, the reactions represented by the follow- 
ing equations take place step by step : — 



METHYL-AMINE. 95 

C 2 H 5 Br +NH 3 = NH 2 (C 2 H 5 ) . HBr ; 

C 2 H 5 Br + NH 2 (C 2 H 5 ) = NH (C 2 H 5 ) 2 . HBr ; 
C 2 H 5 Br +.NH (C 2 H 5 ) 2 = N (C 2 H 5 ) 3 . HBr ; 
C 2 H 5 Br + N (C 2 H 5 ) 3 = N (C 2 H 5 ) 4 Br. 

The first three products are salts of hydrobromic acid, and 
substances which closely resemble ammonia. When these 
salts are distilled with potassium hydroxide they are decom- 
posed, just as ammonium bromide would be. Only instead 
of getting ammonia and potassium bromide, we get the com- 
pounds ethyl-amine, NH 2 .0 2 H 5 , di-ethyl-amine, NH(C 2 H 5 ) 2 , and 
tri-ethyl-amine, 1ST (C 2 H 5 ) 3 . These substances may be regarded 
as derived from ammonia by the replacement of one, two, 
and three of the hydrogen atoms respectively by ethyl. The 
last product of the series of reactions represented above may 
be regarded as ammonium bromide, NH 4 Br, in which all four 
hydrogen atoms are replaced by ethyl groups. 

The decomposition by potassium hydroxide of the first two 
salts is represented thus : — 

NH 2 (C 2 H 5 ).HBr + KOH = NH 2 (C 2 H.->) + KBr + H 2 ; 
M(C 2 H 5 ) 2 . HBr + KOH = NH(C 2 H 5 ),> + KBr + H 2 0. 

Methyl-amine, NHa-CHs. — This compound can be pre- 
pared by treating iodo-methane with ammonia: — 

CH 3 I + NH 3 =NH 2 0ir 3 .HL 

It was first made by treating methyl isocyanate, CH 8 — N— CO, 

with caustic potash : — 

CH 3 - N - 00 + 11,0 = Nil,. (MI, + CO* 

It has been stated that it. is formed by treating hydrocyanic 
acid with nascent hydrogen: — 

HON -ft II = NU, .OH* 



96 DERIVATIVES OF METHANE AND ETHANE. 

It occurs in nature in herring brine, in Mercurialis perennis, 
and is one of the products of the distillation of animal matter 
as well as of wood. 

Methyl-amine is a gas which is easily condensed to a liquid. 
It smells like ammonia. It is, like ammonia, extremely easily 
soluble in water, 1 volume of water at 12.5° taking up 1150 
volumes of the gas. This solution acts almost exactly like 
a solution of ammonia in water. It is strongly alkaline. In 
fact, it is more strongly basic than ammonia. It precipitates 
the metallic hydroxides, but, unlike ammonia, it does not dis- 
solve precipitated hydroxides of nickel, cobalt, and cadmium 
when added in excess. Like ammonia, it dissolves aluminium 
hydroxide. 

Methyl-amine forms salts with acids in the same way that 
ammonia does ; that is, by direct addition. The action towards 
nitric and sulphuric acids takes place in accordance with the 
following equations : — 

KH 2 CH 3 + HK0 3 = NH3CH3.NO3; 
2 NH 2 CH 3 + H 2 S0 4 = (NH 3 CH 3 ) 2 S0 4 . 

These salts are called methyl-ammonium nitrate and methyl- 
ammonium sulphate respectively. 

Di-methyl-amine, NH(CH3)2- — This is formed by heating 
iodo-methane with alcoholic ammonia : — 

2 CH3I + 2 NH 3 = KH(CH 3 ) 2 . HI + NH 4 L 

It is formed, together with methyl-amine, as a product of the 
distillation of wood. 

It is a gas which condenses to a liquid at + 7.2°. Its proper- 
ties are much like those of methyl-amine. 

Tri-methyl-amine, N(CH 3 )3. — Tri-methyl-amine is formed 
as one of the products of the treatment of iodo-methane with 



TRI-METHYL-AMINE. 97 

ammonia. It occurs widely distributed in nature, as in the 
blossoms of the hawthorn, the wild cherry, and the pear. It 
is contained in herring brine, and is a common product of the 
decomposition of organic substances which contain nitrogen. 
It is now obtained in large quantities from the so-called " vin- 
asses." These are the waste liquids obtained in the refining of 
beet sugar. When the " vinasses " are evaporated to dryness, 
tri-methyl-amine is given off among the volatile products. It 
is collected as the hydrochloric acid salt, N(CH 3 ) 3 .HC1, which, 
when heated to 260°, yields ammonia, tri-methyl-amine, and 
chlor-methane : — 

3 N(CH 3 ) 3 .HC1 = 2 N(CH 3 ) 3 + NH 8 + 3 CH 3 C1. 

The chlor-methane is utilized for the purpose of producing low 
temperatures. 

Tri-methyl-amine is a liquid boiling at 9° to 10°. It has a 
strong ammoniacal and fishy odor. It is very soluble in water 
and alcohol, and is a strong base. 

The ethyl-amines are very much like the methyl compounds, 
and hence need not be specially described. 

When tri-ethyl-amine is brought together with iodo-ethane, 
the two unite, forming the compound tetra-ethyl-ammonium 
iodide, N(C 2 H 5 ) 4 I, which is ammonium iodide, in which all four 
hydrogen atoms have been replaced by ethyl groups. If silver 
oxide is added to the aqueous solution of the iodide, silver 
iodide is precipitated'and by evaporation of the liquid crystals 
of tetra-ethyl-ammonium Jiydroxide, N\(\.H : ,\,Oir. are obtained. 
This is plainly the hypothetical ammonium hydroxide, in which 
the four ammonium hydrogens have been replaced by ethyl. 
Its solution acts almost like caustic potash. It is very caustic, 
attracts carbon dioxi de from the air, saponifies (see p. 70) 
ethereal salts, and gives the same precipitates as caustic potash. 
It is so strong a base that neither potassium nor sodium hy- 
droxide can separate it- from its salts. The reactions o\' the 
substituted ammonias above described make it certain that 



98 DERIVATIVES OF METHANE AND ETHANE. 

these bodies are very closely related to ammonia. The 
methods of formation also point clearly to the same con- 
clusion. This relation is best expressed by the formulas 
above given. 

Another method for the formation of substituted ammonias 
in which but one radical is present, as ethyl-amine, NH 2 .C 2 H 5 , 
or in general NH 2 .R, consists in treating with nascent hydro- 
gen compounds known as nitro compounds, which are substi- 
tution-products containing the group N0 2 in the place of 
hydrogen. Thus, for example, when nitro-m ethane, CH 3 .N0 2 
(which see), is treated with hydrogen, the reaction which takes 
place is represented thus : — 

CH 3 .N0 2 + 6 H = CH 3 .KE 2 + 2 H 2 0. 

In connection with another series, it will be shown that this 
reaction is a most important one, from a practical as well as 
a scientific point of view. It may be said in anticipation that 
the manufacture of aniline, and consequently of all the many 
valuable dye-stuffs related to aniline, is based upon this reac- 
tion. 

Just as we may look upon m ethyl-amine and the related com- 
pounds, as ammonia, in which one hydrogen atom is replaced by 
methyl, so also we may regard them, and with equal right, as 
marsh gas, in which hydrogen has been replaced by the group or 
residue ]STH 2 . Owing to the frequency of the occurrence of this 
group in carbon compounds, and for the sake of simplifying 
the nomenclature, the group has been called the amino group, 
and the bodies containing it amino-compounds. Thus the com- 
pound NH 2 .C 2 H 5 may be called either ethyl-amine or amino- 
ethane, etc. 

Similarly, those bodies which contain two hydrocarbon resi- 
dues, as di-ethyl-amine, ]SrH(C 2 H 5 ) 2 , are called imino-compounds, 
and the group NH the imine or imino group. Substituted 
ammonias containing one hydrocarbon residue are called pri- 
mary ammonia bases. Those containing two residues, as di- 



NITROCOMPOUNDS. 99 

ethyl-amine, NH(C 2 H 5 ) 2 , are known as secondary ammonia 
bases, and those containing three residues, as tri-ethyl-amine, 
N(CH 3 )j, are called tertiary ammonia bases. 

Among the most important of the reactions of ammo-com- 
pounds or primary bases is tha,t which takes place when they 
are treated with nitrous acid. Take ethyl-amine as an illustra- 
tion. In order to understand what takes place when this 
compound is treated with nitrous acid, it is necessary to keep 
in mind the fact that the compound itself is a modified ammo- 
nia, and hence we may expect that its reactions will be but 
modifications of those which take place with ammonia. Thus 
with nitrous acid ammonia unites directly to form ammonium 
nitrite : — 

NH 3 + HN0 2 = NH 4 .N0 2 . 

So also ethyl-amine forms ethyl-ammonium nitrite : — 

NH 2 .C 2 H 5 + HN0 2 = NH 3 (C 2 H 5 ).N0 2 . 

Ammonium nitrite breaks up readily into free nitrogen and 

NH 4 . N0 2 = N 2 + H 2 + HoO. 

So also ethyl-ammonium nitrite breaks up into free nitrogen, 
water, and alcohol : — 

NH 3 (C 2 H 5 )N0 2 = No + H 2 + C 2 H 5 .OH. 

The two reactions are strictly analogous. As in the second case 
we start with a substituted ammonia, we get as a product a 
substituted water or alcohol. 

This reaction has been used very extensively in the prepara- 
tion of compounds containing hydroxyl. For ordinary alcohol, 
as is clear, it is not a convenient method of preparation ; but it 
will be shown that there are hydroxides for \ho preparation of 
which it is by far the most convenient method. The essential 
character of the transformation effeoted by it will be best under- 
stood by comparing the formulas of the amino compound and 
the alcohol. We have ethyl-amine, (\ll,. NIU and from it we 

LofC. 



100 DERIVATIVES OF METHANE AND ETHANE. 

get alcohol, C 2 H 5 .OH. Thus we see that the transformation 
consists in replacing the amino group by hydroxyl. 

Hydrazine Compotjxds. 

There is an important class of compounds, the members of 
which bear the same relation to the compound hj'drazine, X 2 H 4 
( HoX — XH 2 ), that the substituted ammonias bear to ammonia. 
The reactions by which they are prepared are somewhat com- 
plicated, and cannot well be discussed at this stage. The best- 
known hydrazines are those related to the hydrocarbons of the 
benzene series, as, for example, phenylhydrazine, C 6 H 5 . Y H . XH,. 

NlTRO-COMPOUUDS. 

Reference has already been made to a class of compounds con- 
taining the group X0 2 , and known as nitro-compounds. They 
are most readily made by treating the hydrocarbons with nitric 
acid. This method, however, is not applicable to the hydro- 
carbons methane and ethane and their homologues, as these are 
not readily changed by nitric acid. The hydrocarbon benzene, 
C 6 H 6 , is very easily acted upon by nitric acid, when the reac- 
tion represented by the following equation takes place : — 

C 6 H 6 + HO . X0 2 = C 6 H 5 . XOo + HoO. 

The action is like that which takes place between sulphuric 
acid and benzene, which gives the sulphonic acid C 6 H 5 .S0 2 OH 

C IT- 

or * * > S0 2 . (See p. 76.) In each case a hydroxyl of the 

acid is replaced by the simple residue of the hydrocarbon. The 
product in the case of the dibasic acid, sulphuric acid, is itself 
still acid, while the product in the case of the monobasic nitric 
acid, is not an acid. 

The nitro-derivatives of methane have been made by a reac- 
tion which we should expect to yield ethereal salts of nitrous 
acid ; namely, by treating iodo-methane or ethane with silver 
nitrite : — 



NITROSO- AND 1SONITROSO-COMPOUNDS. 101 

CH 3 I -f AgN0 2 = CH 3 N0 2 + Agl. 

Tlie compound CH3.NO2, which is known as nitro-methane, 
does not conduct itself like the ethereal salts of nitrous acid. 
Methyl nitrite, CH 3 O.NO, can be saponified; nitro-methane 
cannot. 

Note for Student. — Compare the reaction just referred to with 
that which takes place between silver cyanide and iodo-methane ; and 
that which takes place between iodo-ethane and potassium sulphite. 
What analogy is there to the former and to the latter ? 

It has already been stated that the nitro-derivatives are con- 
verted by nascent hydrogen into the corresponding amino- 
derivatives (see p. 97). 

Note for Student. — Write the equations representing the reactions 
necessary to convert methyl alcohol into methyl-amine by means of the 
nitro-compound. 

Nitroform, CHCNOaK as the formula indicates, is the tri- 
nitro-derivative of methane, or tri-nitro-methane. It is con- 
verted into tetra-nitro-methane, C(N0 2 ) 4 , when treated with a 
mixture of concentrated sulphuric and fuming nitric acids. 

Nitro-chloroform, CCNO^Clo, called also cklorpicrin and 
nitro-trichlormethane, is formed by distilling methyl or ethyl 
alcohol with common salt, saltpetre, and sulphuric acid. It is 
formed from a number of more complicated nitrocompounds, 
by distilling them with bleaching lime or hydrochloric acid and 
potassium chlorate. 

NlTROSO- AND ISONITROSO-COMPOUNDS. 

When a compound containing the group (Ml is treated with 
nitrous acid, a reaction takes place, which is represented thus: — 

R,.( 1 1I + KO.NO = R 3 .C.NO-f U,0. 

The product. R3.C.NO, which is derived from the original sub- 
stance by the substitution o\' the group NO tor a hydrogen 
atom, is called a, nitroso-compouml. I>y oxidation the nitroso- 



102 DERIVATIVES OF METHANE AND ETHANE. 

compounds are converted into nitro-compounds, and by reduc- 
tion they yield the same products as the corresponding nitro- 
compounds, that is to say, the amines. 

The isonitroso-compounds are isomeric with the nitroso-com- 
pounds. They are formed when acetones or aldehydes are 
treated with hydroxylamine, NH 2 .OH. The reaction may be 
represented thus : — 

CH 3 CH 3 

I I 

CO + H 2 N.OH = C = N - OH + H 2 0. 

I I 

CH 3 CH 3 

The hydrogen of the hydroxyl has acid properties. The 
isonitroso-compounds are readily broken up by hydrochloric 
acid, yielding, as one of the products, hydroxylamine. They 
are generally called oximes. 

As hydroxylamine reacts in this way with all aldehydes 
and with all ketones, it is a valuable reagent for compounds 
belonging to these classes. 

Fulminic acid, CNOH, according to recent investiga- 
tions, appears to be an isonitroso-compound, and for that 
reason finds appropriate mention in this place. The principal 
compound of fulminic acid, is the mercury salt, C 2 N 2 2 Hg, 
commonly known as fulminating mercury. It is prepared by 
dissolving mercury in strong nitric acid, and adding alcohol to 
the solution. It is extremely explosive. Mixed with potassium 
nitrate it is used for filling percussion-caps. 

When fulminating mercury is treated with concentrated hydro- 
chloric acid, it yields hydroxylamine as one of the products of 
decomposition. Fulminic acid appears, therefore, to be an 
isonitroso-compound. It is probably the oxime of carbon mon- 
oxide, and should be represented by the formula C = N — OH. 
As will be seen, fulminic acid is isomeric with cyanic and 
cyanuric acids (see pp. 84 and 85). 



CHAPTER VII. 

DERIVATIVES OP METHANE AND ETHANE CON- 
TAINING PHOSPHORUS, ARSENIC, ETC. 

Phosphorus compounds.— Corresponding to the amines or 
substituted ammonias are the phosphines, which, as the name 
implies, are related to phosphine, PH 3 . Methyl-phosphine, 
PH 2 .CH 3 , di-methyl-phosphine, PH(CH 3 ) 2 , and tri-methyl- 
phosphine, P(CH 3 ) 3 , may be taken as examples. 

These substances, like the corresponding amines, form salts 
with acids, though not as readily. The hydroxide, tetra-eihyl- 
phosphonium hydroxide, P(C 2 H 5 ) 4 .OH, is a very strong base, 
though not as strong as the corresponding nitrogen derivative. 

The phosphines have one marked property which distin- 
guishes them from the amines, and that is their power to take 
up oxygen and form acids. Thus, ethyl-phosphine, PH 2 .CoII 5 , 
when treated with nitric acid, is converted into ethyl-phos- 
phinic acid, PO(C 2 H 5 ) (0H) 2 , a dibasic acid, bearing to phos- 
phoric acid the same relation that the sulphonic acids boar to 
sulphuric acid. 

Note for Student. — What is the relation? What other class of 
acids bears the same relation to carbonic acid? 

Di-ethyl-phosphine, PII(C 2 H 5 ) 2 , yields di-ethyl-jphosphinic acid, 
PO(C 2 H 6 ) 2 .OH, when oxidized. 

These compounds are not commonly met with, and do not 
play a very important part in the study of the compounds of 
carbon. 

Arsenic compounds. — The most characteristic oarbos 

compound containing arsenic is that which is known as cacodul. 



104 DERIVATIVES OF METHANE AND ETHANE. 

a name given to it on account of its extremely disagreeable 
odor (from Ka^6 V g, stinking). It is prepared by distilling a mix- 
ture of potassium acetate and arsenic trioxide. The reactions 
which take place are very complicated, aud many products are 
formed. Chief among the products is cacodyl oxide : — 
4 CH 3 .C0 2 K+ As 2 3 = [ (CH 3 ) 2 As] 2 + 2 K 2 C0 3 + 2 C0 2 . 
When treated with hydrochloric acid, the oxide is converted 
imtothe chloride (CH 3 ) 2 AsCl; and, when the chloride is treated 
with zinc, cacodyl itself is produced. Its analysis and the 
determination of its molecular weight lead to the formula 
As 2 C 4 H 12 , which in all probability should be represented thus: 

(CH 3 ) 2 As ) Cacodyl appears thus as a compound analogous 

(CH 3)2 As S 

to the hydrazines referred to above. (See p. 100.) 
Note for Student.— In what does the analogy consist 1 
Many derivatives of cacodyl have been made, but their study 

would hardly be profitable at this stage. 
Zinc ethyl itself is made by treating iodo-ethane, C 2 H 5 I, 

with zinc alone or with zinc sodium. The reaction takes place 

in two stages. First by addition, a compound of the formula 

Zn < is formed. When this is distilled, zinc ethyl and zinc 

C 2 H 5 

iodide are formed : — 

2 Zn<* __ = Zn(C 2 H 5 ) 2 + Znl 2 . 
C 2 H 5 

It is a liquid boiling at 118°. It takes fire in the air, and burns 
with, a white flame. 

Sodium ethyl, C 2 H 5 Na, can be obtained in combination 
with zinc ethyl by treating the latter with sodium. Both these 
compounds have been used to a considerable extent in the syn- 
thesis of carbon compounds, particularly the more complex 
hydrocarbons, and they will be frequently referred to in the 
following pages. 



RETROSPECT. 105 

Note for Student. — What is formed when sodium methyl and 
carbon dioxide are allowed to act upon each other? 

Many of the derivatives, like the above, are volatile liquids. 
Such, for example, are mercury ethyl, Hg(C 2 H 5 ) 2 , aluminium 
etlrrl, A1(C 2 H 5 ) 3 , tin tetrethyl, Sn(C 2 H 5 ) 4 , and silicon tetrethyl, 
Si(C 2 H 5 ) 4 . The study of these compounds has been of assist- 
ance in enabling chemists to determine the atomic weights of 
some of the elements which do not form simple volatile 
compounds. 

Retrospect. 

In the introductory chapter (p. 19) these words were used in 
describing the plan to be followed: "Of the first series of 
hydrocarbons two members will be considered. Then the de- 
rivatives of these two will be taken up. These derivatives will 
serve admirably as representatives of the corresponding deriva- 
tives of other hydrocarbons of the same series and of other 
series. Their characteristics and their relations to the hydro- 
carbons will be dwelt upon, as well as their relations to each 
other. Thus, by a comparatively close study of two hydro- 
carbons and their derivatives, we may acquire a knowledge of 
the principal classes of the compounds of carbon. After these 
typical derivatives have been considered, the entire series of 
lrydrocarbons will be taken up briefly, only such facts being 
dealt with at all fully as are not illustrated by the first two 
members." 

In accordance with the plan thus sketched we have thus far 
studied the principal derivatives of the two hydrocarbons, 
methane and ethane, so far as these derivatives represent dis- 
tinct classes of compounds. These derivatives were classified 
first into (1) those containing halogens ; (2) those containing 
oxygen; (8) those containing sulphur ; and (4) those contain- 
ing nitrogen. On examining each o( these classes more closely, 
we found that the halogen derivatives, such as I'hlor-methane. 
brom-ethane, etc., bear very simple relations bo each other. 



106 DERIVATIVES OF METHANE AND ETHANE. 

We found that under the head of oxygen derivatives, the most 
important and most distinctly characteristic derivatives of 
hydrocarbons are met with; as, the alcohols, ethers, aldehydes, 
acids, ethereal salts, and ketones. The sulphur derivatives, 
some of which closely resemble the oxygen derivatives, include 
the sulphur alcohols or mercaptans, sulphur ethers, and sulphonic 
acids. 

On beginning the consideration of the nitrogen derivatives 
we found it desirable first to take up certain derivatives con- 
taining the cyanogen group, among which are cyanogen, hydro- 
C}^anic acid, cyanic acid, and sulphocyanic acid. Many interest- 
ing carbon compounds are closely related to these fundamental 
compounds. Such, for example, are the cyanides and isocy- 
anides, the cyanates and isocyanates, the sulpho-cyanates and 
iso-sulpho-cyanates or mustard-oils. Following the compounds 
related to cyanogen, we took up the interesting compounds 
which are related to ammonia, the substituted ammonias or 
amines. Then came the nitro-derivatives ; and, finally, the 
compounds of the hydrocarbon residues or radicals with metals. 

It is of the greatest importance that the student should 
master the preceding portion of this book. If he studies 
carefully the reactions that have been treated of, which are 
statements in chemical language that tell us the conduct of 
the various classes of derivatives, and if he performs the ex- 
periments which have been described, he will have a fair general 
knowledge of the kinds of relations which are met with in con- 
nection with the compounds of carbon through the whole field. 
As stated in the Introduction : "If we know what derivatives 
one Irydrocarbon can yield, we know what derivatives we may 
expect to find in the case of every other hydrocarbon. " 

The more the student practises the use of the equations thus 
far given, the better he will be prepared to follow the remain- 
ing portions of the book. Indeed, it may be said that, if he 
thoroughly understands what has gone before, what follows will 
appear extremely simple. Whereas, if he has failed at any 



RETROSPECT. 107 

point to catch the exact meaning, if he has failed to see the 
connection, he had better go back and faithfully review, or he 
will soon find his mind hopelessly muddled, and relations which 
are as clear as day will be concealed from him. 

An excellent practice is to trace connections between the 
different classes of compounds, and show how to pass from one 
to the other. Thus, for example, (1) show by what reactions 
it is possible to pass from marsh gas to acetic acid. (2) How 
can we pass from ordinary alcohol to ethylidene chloride, 
CH 3 .CHC1 2 ? (3) What reactions would enable us to make 
methyl-amine from its elements? (4) How can acetone be 
made from methyl-amine ? (5) What reactions are necessary in 
order to make ordinary ether from ethyl-amine? etc., etc. It 
is well in this sort of practice to select what appear to be the 
least closely -related compounds, and to show then how we can 
pass from one to the other. Be sure to select representatives 
of all the classes hitherto mentioned, and to bring in all the 
important reactions. 



CHAPTER VIII. 

THE HYDROCARBONS OF THE MARSH-GAS 
SERIES, OR PARAFFINS. 

The existence of the homologous series of lrydrocarbons be- 
ginning with methane and ethane was spoken of before its first 
two members were considered. A general idea of the extent 
of the series, and of the names used to designate the members, 
may be gained from the following table : — 



MARSH-GAS 


HYDROCARBONS 




Paraffins 


. — Hydrocarbons, 


^nH2 n + 2« 












Boiling-Point. 


Methane 


. 


. CH 4 


. 




. gas. 


Ethane . 


. 


. C 2 H 6 


. 




. gas. 


Propane 


. • 


• C 3 H 8 


. 




. gas. 


Butane (normal) 


. C 4 H 10 


. 




. 1°. 


Pentane l 




. CsH^ 


. 




37°. 


Hexane i 




• C 6 Hu 


. 




69°. 


Heptane ' 




• C 7 H 16 


. 




98°. 


Octane ' 




. C 8 H 18 


. 




125°. 


Nonane ' 




Ly 9 H 20 


. 




150°. 


Dodecane ' 




• C ]2 H 2 6 


. 




214°. 


Hexadecane ' 




• C 16 H34 






287°. 



The explanation of the remarkable relation in composition 
existing between these members, a relation to which the name 
homology is given, has already been referred to (p. 22) . The 
number of hydrogen atoms contained in a member of this series 



PETROLEUM. 109 

bears a constant relation to the number of carbon atoms, as 
expressed in the general formula C n H 2n+2 . On examining the 
column headed " Boiling Point " it will be seen that, as we pass 
upward in the series, the boiling-point becomes higher and higher. 
The first three members are gases at ordinary temperatures, 
while the last boils at 287°. The elevation in the boiling-point 
is to some extent regular, as will be observed. The difference 
between butane, C 4 H 10 , and pentane, C 5 H 12 , is 37 — 1 = 36° ; 
that between pentane and the next member is 69 — 37 = 32° ; 
between hexane and heptane it is 98 — 69 = 29° ; between 
heptane and octane, 125 — 98 — 27° ; and, finally, between 
octane and nonane the difference is 150 — 125 = 25°. Thus it 
will be seen that the elevation in boiling-point caused by the 
addition of CH 2 decreases as we pass upward in the series. 
Other relations have been pointed out, but it would be prema- 
ture to discuss them here. 

The chief natural source of the paraffins is petroleum ; but 
although this substance, which occurs in such enormous quanti- 
ties in nature, undoubtedly contains a number of the members 
of the paraffin series, it is an extremely difficult matter to 
isolate them from the mixture. Prolonged fractional distilla- 
tion is not sufficient for the purpose. If, however, some of the 
purest products which can thus be obtained arc treated with 
concentrated sulphuric acid, and afterwards with concentrated 
nitric acid, and then washed and redistilled, they can be 
obtained in pure condition. 

Petroleum. — Petroleum occurs in enormous quantities in 
several places. Among the most important localities are 
Pennsylvania, the Crimea, the Caucasus, Persia, Burmah, 
China, etc. In some places it issues constantly from the 
earth. Usually it is necessary to bore for it. When one o\ 
the cavities in which it is contained is punctured, the oil 
is forced out of a pipe inserted into the opening in a jet, in 
consequence of the pressure exerted upon its surface. As 



110 HYDROCARBONS OF THE MARSH-GAS SERIES. 

first obtained, it is usually a dark, yellowish-green liquid, with 
an unpleasant odor. It varies in appearance according to the 
place where it is found. American petroleum contains the 
lowest members of the paraffin series ; and when the oil is 
exposed to the air the gases are given off. 

Refining of petroleum. To render petroleum fit for use in 
lamps, it is necessary that the volatile portions should be 
removed, as they form explosive mixtures with air, just as 
marsh gas does. It is also necessary to remove the higher 
boiling portions, because they are semi-solid, and would clog 
the wicks of the lamps. The crude oil is therefore subjected to 
distillation, and only those parts which have a certain specific 
gravity or boil between certain points are used for illuminating 
purposes, under the name of kerosene. Besides being distilled, 
the oil must further be treated with concentrated sulphuric 
acid, which removes a number of undesirable substances, and 
afterwards with an alkali, and then with water. All these 
processes taken together constitute what is called the refining 
of petroleum. In the distillation, the lighter products are 
usually divided into several parts, according to the specific 
gravity or boiling-point. Thus we have the products cymogene, 
rhigolene, gasoline, naphtha, and benzine, all of which are 
lighter than kerosene. It must be distinctly understood that 
the substances here mentioned are not pure chemical indi- 
viduals. The names are commercial names, each of which 
applies to a complex mixture of hydrocarbons. From the 
heavier products, that is, those that boil at higher tempera- 
tures than the highest limit for kerosene, paraffin, which is a 
mixture of the highest members of this series, is made. 

Owing to the danger attendant upon the use of improperly 
refined petroleum, laws have been enacted relating to the 
properties which the kerosene exposed for sale must have. 
These laws, which differ somewhat in different countries and 
different parts of the same country, relate mostly to what is 
sailed the flashing -point. This is the temperature to which the 



SYNTHESIS OF THE PARAFFINS. 



Ill 



d 



6 

-A 



oil must be heated before it takes fire when a flame is applied 
to it. The legal flashing-point in many parts of the United 
States is 44°. A simple and accurate instrument for deter- 
mining the flashing-point is here described : The cylinder A 
is at least 2.5 cm in diameter, and at least 16 cm long. Just 
within the cork the bent tube contracts 
to a small orifice. At d it is connected 
with a hand-bellows or a gas-holder ; and 
the flow of air is controlled by a pinch- 
cock. The cylinder is filled with oil to 
a point such that, when the air is run- 
ning, the surface of the foam is about 
5 cm from the top ; and it is then put 
in a beaker of water to the level of the oil. 
Air is now passed through deb, and e so 
adjusted that about 0.5 cm foam is kept 
on the surface of the oil. From degree to degree the test is 
made by bringing a small flame for an instant to the mouth of 
A. At the flashing-point the vapor ignites, and the bluish flame 
runs down to the surface of the oil. 



5s^ 

n 



Fig. 9. 



Experiment 31. Make an apparatus like the above, and determine 
the flashing-points of two or three specimens of kerosene that may be 
available. 

Synthesis of the paraffins. — Although the paraffins occur 
in nature, and a few of them can be obtained in pure condition 
from natural sources, we are dependent upon synthetical oper- 
ations performed in the laboratory for our knowledge of the 
series and the relations existing between them. 

We have already seen how ethane can be prepared from 
methane by treating methyl iodide with zinc or sodium, as 
represented in this equation : — 



CII 3 T -f CHgl + 2 Na = C 8 H 6 + 2 NaT 



112 HYDROCARBONS OF THE MARSH-GAS SERIES. 

This method has been extensively used in the building up of 
higher members of the series. Thus from ethane we can make 
ethyl iodide, and by treating this with sodium get butane 
C 4 H 10 : — 

C 2 H 5 I + C 2 H 5 I + 2 Na = C 4 H 10 + 2 Nal. 

But we can get the intermediate member, propane, C 3 H 8 , by 
mixing methyl iodide and ethyl iodide and treating the mixture 
with sodium : — 

CH 3 I + C 2 H 5 I + 2 Na = CH 3 .C 2 H 5 + 2 Nal. 

By applying this method, it is plain that a large number of the 
members of the paraffin series might be made. 

Another method consists in treating the zinc compounds of 
the radicals, like zidc ethyl, Zn(C 2 H 5 ) 2 , with the iodides of rad- 
icals. Thus zinc methyl and methyl iodide give ethane ; zinc 
ethyl and ethyl iodide give butane; zinc ethyl and methyl 
iodide give propane, etc. : — 

Zn(CH 3 ) 2 + 2 CH3I = 2 C 2 H 6 + Znl 2 ; 
Zn(C 2 H 5 ) 2 + 2 C 2 H 5 I = 2 C 4 H 10 + Znl 2 ; 
Zn(C 2 H 5 ) 2 + 2 CH3I = 2 C 3 H 8 + Znl 2 . 

Paraffins can be made by replacing the halogen in a substitu- 
tion-product by hydrogen. This can be effected by nascent 
hydrogen or by hydriodic acid : — 

C 4 H 9 I + 2 H = C 4 H 10 + HI. 

As these halogen substitution-products can easily be made 
from the alcohols, it follows that the hydrocarbons can be made 
from the corresponding alcohols. Finally, the paraffins can be 
made by heating the acids of the formic acid series with an 
alkali. This has been illustrated by the preparation of marsh 
gas from acetic acid by heating with lime and caustic potash. 
The reaction may be written thus : — 

CH 3 .C0 2 K + KOH = CH 4 + C0 3 K 2 . 

The products are a hydrocarbon and a carbonate. 



ISOMERISM AMONG THE PARAFFINS. 113 

Isomerism among" the paraffins. — It has already been 
stated that the evidence is almost conclusive that each of the 
four hydrogen atoms of marsh gas bears the same relation to the 
carbon, and hence we believe that, as regards the nature cf the 
product, it makes no difference which hydrogen atom is replaced 
by a given atom or radical. According to this, as ethane is the 
methyl derivative of marsh gas, it makes no difference which of 
the hydrogen atoms of marsh gas is replaced by the methyl, the 
product must always be the same, or there is but one ethane 

possible according to the theory. This is represented by the 

H H 

I I 
formula, H — C — C — H, or H 3 C — CH r In ethane, as well as in 

I I 

H H 
methane, all the hydrogen atoms bear the same relation to 
the molecule, and it should make no difference which one is 
replaced by methyl. But propane is regarded as derived from 
ethane by the substitution of methyl for hydrogen; and, as it 
makes no difference which hydrogen is replaced, there is but 
one propane possible. Only one has ever been discovered, and 
this must be represented thus : — 

H H H 

I I I 
H-C-C-C-H, or CH3.CH0.CH3. 

I I I 
H H H 
Now, continuing the process of substitution of methyl for hydro- 
gen, it appears that the theory indicates the possibility of the 
existence of two compounds of the formula C 4 H 10 , One of 
these should be obtained by substituting methyl for one of the 
three hydrogens of either methyl group of propane. It is 
represented by the formula, : — 

H II II II 

till 
H-C-C-C-C-H, or 11 c.Ul ,ril ,ril .. 

I II I 
II 11 11 11 



114 HYDROCARBONS OF THE MARSH-GAS SERIES. 

The other should be obtained by substituting methyl for one 
of the two hydrogens of the group CH 2 contained in propane. 
This would give a hydrocarbon of the formula : — 

H H H CH 3 

III I 

H - C - C - C - H, or CH 3 - CH - CH 3 

I I I 
H C H 

/l\ 
H H H 

The theory then indicates the existence of two butanes. How 
about the facts ? Two, and only two, butanes have been discov- 
ered. The first, which occurs in American petroleum, has been 
made synthetically by treating ethyl iodide with zinc : — 

2 CH 3 . CH 2 I + Zn = CH 3 . CH 2 . CH 2 . CH 3 + Znl 2 . 

The method of synthesis clearly shows which of the two possi- 
ble isomerides the product is. It is known as normal butane. 
It is a gas that can be condensed to a liquid at + 1°. 

The second, or isobutane, is made from an alcohol which 
will be shown to have the structure represented by the formula 
CH 3 
I 
CH 3 - C - OH (see Tertiary Butyl Alcohol, p. 124), by replacing 
I 

CH 3 
the hydroxyl by hydrogen. It is a gas that becomes liquid 
at -17°. 

The differences between the two butanes are observed princi- 
pally in their derivatives. 

Applying the same method of reasoning to the next member 
of the series, how many isomeric varieties of pentane, C 5 H 12 , 
may we expect to find ? The question resolves itself into a 
determination of the number of kinds of hydrogen atoms con- 
tained in the two butanes, or the number of relations to the 
molecule represented among the hydrogen atoms of the butanes. 



PENTANES. 115 

"We can make this determination best by examining the struc- 
tural formulas. Take first normal butane : — 

H H H H 

I I I I 

H-C-C-C-C-H. 

Till 

H H H H 

In this there are plainly two different relations represented ; 
viz., that of each of the six hydrogens in the two methyl groups, 
and that of each of the four hydrogens of the two CH 2 groups. 
The two possible methyl derivatives of a hydrocarbon of this 
formula are therefore to be represented thus : — 

H 3 .OH2 -CH^ .CH 2 .CH 3 , (lj 

and H 3 C.CH 2 .CH<™ 3 . (2) 

UH 3 

CH 3 

Now, taking isobutane, HC — CH 3 , we see that it consists of 

I 

. . CH 3. 

three methyl groups, giving nine hydrogen atoms of the same 
kind, and one CH group, the hydrogen of which bears a dif- 
ferent relation to the molecule from that which the other nine 
do. There are therefore two possible methyl derivatives of 
isobutane which must be represented thus : — 

CH 3 CH 3 

I I 

HC - CH,.CH 3 (3), and H ;5 C - C - CI I,. (4) 

I I 

CH 3 CHa 

We have, therefore, apparently four pentanes. But on compar- 
ing formulas (2) and (8), [twill be seen that, though written a 
little differently, they really represent one and the same com- 
pound. Thus the uumber o\' pentanes, the existence of which 
is indicated by the theory, is three, and these arc represented 



116 HYDROCARBONS OF THE MARSH-GAS SERIES. 

by formulas (1), (2), and (4). They are all known. The 
first is called normal pentane, the second iso-pentane or 
di-methyl-ethyl-methane, and the third tetra-methyl-me- 
thane. 

It would lead too far to discuss all the methods of prepara- 
tion and the properties of these hydrocarbons. It will be seen 
that the methods of preparation show what the structure of a 
lrydrocarbon is. Di-methyl-ethyl-methane is made from an 
alcohol which can be shown to have the formula 

^ 3 >CH.CH 2 .CH 2 OH, 
CH 3 

by replacing the hrydroxyl by hydrogen. Hence its structure is 
that represented above by formulas (2) and (3). 

Tetra-methyl-methane is made by starting with acetone. 
Acetone has been shown to consist of carbonyl in combina- 
tion with two methyl groups, as represented in the formula 
CH 3 — CO— CH 3 . It has also been shown that, by treating 
acetone with phosphorus pentachloride, the oxygen is replaced 
by chlorine, giving a compound of the formula CH 3 — CC1 2 — CH 3 . 
Now, by treating this chloride with zinc-methyl, the chlorine is 
replaced by methyl thus : — 



CH 



CH 3 -CC1 2 -CH 3 + Zn(CH 3 ) 2 = CH 3 -C-CH 3 + ZnCl 2 . 

I 
CH 3 

The product is tetra-methyl-methane, and the synthesis thus 
effected shows at once what the structure of the product is. 

Hexanes. — The student will now be prepared to apply the 
theory to the determination of the number of hexanes possible. 
He will find that there are five. The theor} T is, in this case as in 
the preceding, in perfect accordance with the facts. There are 
five and only five hexanes known. Only the names and formu* 
las of these will be given here : — 



HEXANES. 117 

1. Normal hexane, CH 3 .CH 2 .CH 2 .CH 2 .CH 2 .CH 3 . 

2. Iso-hexane, CH 3 .CH 2 .CH 2 .CH < ^ 3 . 

CH S 

3. Methyl-di-ethyl-methane, CH 3 .CH< CH 2- CH 3 f 

CyM 2 .C/H. 3 

4. Tetra-methyl-ethane, ^>HC-CH<^ 3 . 

H 3 U CIi 3 

CH 3 

I 

5. Tri-methyl-ethyl-methane, H 3 C — C — CH 2 .CH 3 . 

I 
CH 3 

Passing upward, we find that nine heptanes are possible 
according to the theory, while but five have thus far been 
discovered ; and that, while theory indicates the possibility of 
the discovery of eighteen hydrocarbons of the formula C S H 18 , but 
two are known. The theoretical number of isomeric varieties 
of the highest members of the series is very great, but our 
knowledge in regard to these highest members is very limited, 
and it is impossible to say whether the theory will ever be 
confirmed by facts. It may be that there is some law limiting 
the number of complicated hydrocarbons. It is, however, idle 
to speculate upon the subject. It is well for us to keep in 
mind that a thorough knowledge of a few of the simplest 
members of the series is all that is necessary for the present. 

On examining the formulas used to express the structure of 
the hydrocarbons, we find that they can be divided into three 
classes : — 

(1) Those in which there is qo carbon atom in combination 
with more than two others ; as, — 

Propane .... CII,.CII...ril. 5 ; 

Normal butane . . Cll, .( 1 1 , .Cll . .CI I , : 

Normal pentane . (1 1, .Cll . .Cll . .Cll, .Cll, : 

and Normal hexane. . Cll, .Cll, .Cll, .Cll... C1C. Cll .. 



118 HYDROCARBONS OF THE MARSH-GAS SERIES. 

(2) Those in which there is at least one carbon atom in 
combination with three others; as, — 

Isobutane . . . . CH 3 .CH < CHs ; 
3 CH 3 ' 

Isopentane . ... CH 3 .CH 2 .CH< CHs ; 

CH 3 

Isohexane . . . . CH 3 .CH 2 .CH 2 .CH < CH;? ; 

CH 3 

and Tetra-methyl-ethane, H ^ > CH-CH < ^ Hs . 

H 3 C CH 3 

(3) Those in which there is at least one carbon atom in 
combination with four others; as, — 



Tetra-methyl- 
methane 



CH 3 

I 
C H 3 — O — CH 3 ; 

I 
CH, 



CH 3 

CH 3 

The members of the first class are called normal paraffins; 
those of the second class, iso -paraffins ; and those of the third 
class, neo-paraffins. 

Only the members of tlie same class are strictly comparable 
with each other. Thus it has been found that the boiling-points 
of the normal hydrocarbons bear simple relations to each other, 
and that the same is true of the iso-paraffins ; but, on compar- 
ing the boiling-points and other physical properties of normal 
paraffins with those of the iso- or neo-paraffins, no such simple 
relations are observed. 



NOMENCLATURE. 119 

Regarding the names of the paraffins, the simplest nomen- 
clature in use is that according to which the hydrocarbons are 
all regarded as derivatives of methane. Thus we get the 

fC 2 H 5 

TT 

name ethyl-methane for propane, C -j „ ; tri-methyl-methane 
f CH 3 I H r CH 3 

for isobutane, C -j ~ 3 ; tetra-methyl-methane, C i rR 3 , etc. 

I H 3 I Ch! 



CHAPTER IX. 

OXYGEN DERIVATIVES OF THE HIGHER MEM- 
BERS OF THE PARAFFIN SERIES. 

We are now to take up the derivatives of the higher mem- 
bers of the paraffin series, just as we took up the derivatives of 
methane and ethane. Not much need be said in regard to the 
halogen derivatives. A few of them will be mentioned in con- 
nection with the corresponding alcohols. The chief substances 
that will require attention are the alcohols and acids. 

1. Alcohols. 

Normal propyl alcohol, Propanol, C3H7OH. — When 
sugar undergoes fermentation, a little propyl alcohol is always 
formed, and is contained in the " fusel oil." From this it can 
be separated by treating those portions which boil between 
85° and 110° with phosphorus and bromine. The bromides of 
the alcohols present are thus formed (what is the reaction ?), 
and these are separated by fractional distillation. The bro- 
mide corresponding to propyl alcohol is then converted into 
the alcohol (how can this be done ?). 

It is a colorless liquid with a pleasant odor. It boils at 97° 
(compare with the boiling-points of methyl and ethyl alcohol). 
It conducts itself almost exactly like the first two members 
of the series. By oxidation it is converted into an aldehyde, 
C 3 H 6 0, and an acid, C 3 H 6 0o, which bear to it the same relations 
that acetic aldehyde and acetic acid bear to ethyl alcohol. 

Secondary propyl or isopropyl alcohol, C3H7.OH. — 

The reasons for regarding the alcohols as hydroxyl derivatives 



SECONDARY ALCOHOLS. 121 

of the hydrocarbons have been given pretty fully. As the six 
hydrogen atoms of ethane are all of the same kind, but one 
ethyl alcohol appears to be possible and only one is known. 
But just as there are two butanes or methyl derivatives of pro- 
pane, so there are two hydroxy 1 derivatives of propane ; or, in 
other words, two propyl alcohols. The first is the one obtained 
from "fusel oil," the other is the one called secondary propyl 
alcohol. This has already been referred to under the head of 
Acetone (see p. 72), where it was stated that acetone is con- 
verted into secondary propyl alcohol by nascent hydrogen. 
We are, in fact, dependent upon this method for the prepara- 
tion of the alcohol. 

It is, like ordinary propyl alcohol, a colorless liquid. It 
boils at 81°. While all its reactions show that it is a hydroxide, 
under the influence of oxidizing agents it conducts itself quite 
differently from the alcohols thus far considered. It is con- 
verted first into acetone, C 3 H 6 0, which is isomeric with the 
aldehyde obtained from ordinary propyl alcohol ; by further 
oxidation, it however does not yield an acid of the formula 
C 3 H 6 2 , as we should expect it to, but breaks down, yielding- 
two simpler acids; viz., formic acid, CELCX,, and acetic acid. 
C 2 H 4 2 . 

Secondary alcohols. — Secondary propyl alcohol is the 
simplest representative of a class of alcohols that are known 
as secondary alcohols. They arc made by treating the ketones 
with nascent hydrogen, and are easily distinguished from other 
alcohols by their conduct towards oxidizing agents. They 
yield acetones containing the same number of carbon atoms. 
and then break down, yielding acids containing :i smaller num- 
ber of carbon atoms. 

Is there anything in the structure of these secondary alcohols 
to suggest an explanation of their conduct? Secondary pro- 
pyl alcohol is made from acetone h\ treating with nascent 
hydrogen. Acetone conlains hvo methyl groups and carbonvl, 



122 DERIVATIVES OF THE PARAFFINS. 

as represented by the formula CH 3 — CO — CH 3 c The sim- 
plest change that we can imagine as taking place in this com- 
pound under the influence of hydrogen is that represented in 
the following equation : — 

CH3-CO-CH3 + H 2 = CH3-CH.OH-CH3. 

The very close connection existing between acetone and second- 
ary propyl alcohol, and the fact that there are two methyl 
groups in acetone, make it appear probable that there are also 
two metlryl groups in secondary propyl alcohol, as represented 
in the above equation. On the other hand, the easy transfor- 
mation of primary propyl alcohol into propionic acid, which can 
be shown to contain ethyl, shows that in the alcohol ethyl is 
present. Therefore, we may conclude that the difference 
between primary and secondary propyl alcohol is that the 
former is an ethyl derivative and the latter a di-methyl deriva- 
tive of methyl alcohol, as represented by the formulas : — 





f H 


C CH 2 'CH 3 




rCH 3 


c< 


H 
H 


° s 


c< 


CH 8 
H 


Meth) 


^OH 

d alcohol. 


^OH 

Ethyl-methyl alcohol or 
ordinary propyl al- 
cohol. 


Dimeth; 

hoi 

prop 


^OH 

i-methyl alco- 
r secondary 
yl alcohol. 



Primary propyl alcohol is methyl alcohol in which one hydrogen 
is replaced by a radical, while secondary propyl alcohol is 
methyl alcohol in which two hydrogens are replaced by radicals. 
An examination of all secondary alcohols known shows that 
the above statement can be made in regard to all of them. 
They must be regarded as derived from methyl alcohol by the 
replacement of two hydrogen atoms by radicals. The alcohols 
of the first class, like methyl, ethyl, and ordinary propyl alco- 
hols, which are derived from methyl alcohol by the replacement 
of one hydrogen by a radical, are called primary alcohols. 
Another way of stating the difference between primary and 



BUTYL ALCOHOLS. 123 

secondary alcohols is this : Primary alcohols contain the group 
CH 2 OH ; secondary alcohols contain the group CHOH. These 
statements necessarily follow from the first ones. 

A primary alcohol, when oxidized, yields an aldehyde and 
an acid containing the same number of carbon atoms as the 
alcohol. 

A secondary alcohol, when oxidized, yields an acetone, and 
then an acid or acids containing a smaller number of carbon 
atoms. 

Recalling what was said regarding the nature of the changes 
involved in passing from an alcohol to the corresponding alde- 
hyde and acid, it will be seen that the formation of the acid is 
impossible in the case of a secondary alcohol. In the case of 
a primary alcohol, we have: — 

R ( R rR 

H 



C \ H C X OH. 

H lo lo 

OH 

Alcohol. Aldehyde. Acid. 

In the case of the secondary alcohol, we have : — 

■is. -6 

Secondary alcohol. Ketone. 

Further introduction of oxygen cannot take place without a 
breaking down of the compound. It will be Been that the 
formulas used to express the structure of the compounds arc 
remarkably in accordance with the facts. 

Butyl alcohols, C,H.,. OH. — Theoretically, there 1 are two 
possible hydroxyl derivatives of each o( the two butanes, 

making four butyl alcohols in all. Thev arc all known. Two 
are primary alcohols. 



124 DERIVATIVES OF THE PARAFFINS. 

1. Normal butyl alcohol, CH 3 .CH 2 .CH 2 .CH 2 .OH. 

pTT 

2. Isobutyl alcohol, ~* 3 >CH.CH 2 OH. 

CH 3 

The third is a derivative of normal butane, and is a secondary 
alcohol. 

3 Secondary butyl alcohol, CH 3 .CH 2 .CH< 0H . This 

CH 3 

alcohol is prepared by treating ethyl-methyl ketone with nascent 
hydrogen : — 

CH 3 .CH 2 -CO-CH 3 + H 2 = CH 3 .CH 2 .CH< OH . 

CH 3 

(Compare this with the reaction for making secondary propyl 
alcohol.) CH, 

I 3 
4. Tertiary butyl alcohol, CH 3 - C - OH. The f ourth butyl 

CH 3 
alcohol has properties which distinguish it from the primary and 
secondary alcohols. When oxidized it yields neither an alde- 
hyde nor an acetone, but breaks down at once, yielding acids con- 
taining a smaller number of carbon atoms. Assuming that every 
primary alcohol contains the group CH 2 OH, and that every sec- 
ondary alcohol contains the group CHOH, it follows that the two 
primary butyl alcohols and secondary butyl alcohol must have 

the formulas above assigned to them ; and it follows further, that 

CH, 
I 
the fourth butyl alcohol must have the formula CH 3 — C — OH, 

CH 3 
as this represents the only other arrangement of the constituents 
possible, according to our theory 7 . This formula represents a 
condition which does not exist in either the primary or second- 
ary alcohols. It is methyl alcohol in which all the hydrogen 
atoms, except that in the hydroxyl, are replaced by methyl 
groups, and it contains the group C — (OH). Such an alcohol 
is known as a tertiary alcohol, and the one under consideration 



PENTYL ALCOHOLS. 125 

is called tertiary butyl alcohol. It is the simplest derivative of 
a class of which, but few members are known. 

Tertiary butyl alcohol is made by treating acetyl chloride, 
CH3.COCI, with zinc methyl, Zn(CH 3 ) 2 . These two substances 
unite, forming a crystallized compound; and, when this is 
treated with water, it breaks up, yielding acetone : — 

f CHs 
CH 3 .C^^+ Zn(CH 3 ) 2 = CH 3 .C 1 O.Z11CH3 ; 

fCH 3 
CH 3 .C i OZnCH 3 + 2 H 2 = CH 3 .CO.CH 3 + Zn(OH) 2 + HC1 + CH 4 . 

I CI 

If, however, a second molecule of zinc methyl reacts upon the 
product first formed, the change represented by the following 
equation takes place : — 

f CH 3 r CH 3 

CH 3 .C \ OZnCH 3 + Zn(CH 3 ) 2 = CH 3 .C \ OZnCH 3 + Zn < )?_ . 

L ci Ich 3 CH:5 

By treating the product with water, tertiary butyl alcohol is 
formed : — 

CH 3 r CH 3 



CH 3 .C -j OZ11CH3 + 2 H 2 = CII3.C 1 OH + Zn(OH) 2 + CH 4 . 
CH 3 I CH 8 

By taking other acid chlorides, and the zinc compounds of 
other radicals, other tertiary alcohols may be obtained. 

Characteristics of the three Classes of Alcohols. To recapitu- 
late briefly, the hydroxyl derivatives of the hydrocarbons can 
be divided into three classes, according bo their conducl towards 
oxidizing agents. 

To what was said above regarding the conduct o( primary and 
secondary alcohols we can new add: Tertiary alcohols yield 
neither aldehydes nor acetones containing the same number of 
carbon atoms, but generally break down, yielding simpler acids. 

The general formulas representing the three classes of alco- 
hols are : — 



126 DERIVATIVES OF THE PARAFFINS. 



E 




f 



C i tt and 




OH 

Secondary. 

Pentyl alcohols, C5H11.OH. — Eight of these are possible, 
and seven are known. Only the two amyl alcohols need be 
taken up here. 

Inactive amyl alcohol, ^S 3 > CH ~ 0H 2 - CH2OH. — 

CH3 

This alcohol, together with at least one other of the same com- 
position, forms the chief part of "fusel oil." By fractional 
distillation of this, ordinary amyl alcohol is obtained, as a color- 
less liquid, having a penetrating odor, and boiling at 131° to 
132°. This can be separated by other methods into two isomeric 
alcohols, one of which is inactive amyl alcohol and the other 
active amyl alcohol. The names refer to the behavior of the 
substances towards polarized light, the former having no action 
upon it, the latter turning the plane of polarization to the left. 
When oxidized, inactive amyl alcohol yields an acid contain- 
ing the same number of carbon atoms, and is, therefore, a 
primary alcohol. The acid has been made by simple reac- 
tions which show that it must be represented by the formula 

nTT 3 >CH.CH 2 .C0 2 H. Therefore, the alcohol has the structure 

3 CH 

represented by the formula CH 8 >CH.CH 2 .CH 2 OH. 

prr 

Active amyl alcohol, CH 3 .CH 2 .CH< cHsOH' - ™ s? as 

has been stated, is obtained, together with the inactive alcohol, 
from fusel oil. It is a primary alcohol as represented. 

A list of some of the more important remaining mem- 
bers of the series is given below. In naming the alcohols, 
it is best to refer them to methyl alcohol, just as the 
hydrocarbons are referred to marsh gas. Calling methyl 
alcohol carbinol, we get such names as methyl-carbinol, 
di-ethyl-carbinol, etc., which convey at once an accurate idea 



NOMENCLATURE. 



127 



concerning the structure of the substances. A few illustrations 
will suffice. Take the alcohols considered above : — 



Ethyl alcohol is methyl-carbinol, 



CH 3 
H 

H ; 
OH 

CH2^Hg 

TT 

Primary propyl alcohol is ethyl-carbinol, C-j ; 

OH 

CH 3 

Secondary propyl alcohol is di-methyl- \ ^ J CH 3 

I I H ; 



carbinol. 



Tertiary butyl alcohol is tri-methyl-carbinol, C 



Inactive amyl alcohol is isobutyl-carbinol, C 



OH 

CH 3 
CH 3 . 
CH 3 ' 
OH 

fCH 2 .CH< 

II 
II 



CH S 
CH, 



I OH, etc., etc., 
a name given to it on account of the presence in it of the iso- 

butyl group CIT. 2 .CII < CH • 

The following table will give an imperfect idea, of the extent 
to which the series of alcohols derived from the paraffins is 
developed. There are thirteen hexyl alcohols and thirteen heptvl 
alcohols known. Of most oi' the higher members but cue 
variety is known. They are not important, except in so far 
as they indicate the possibility of the discovery of other 
alcohols. 



128 DERIVATIVES OF THE PARAFFINS. 

ALCOHOLS OF THE METHYL ALCOHOL SERIES. 
Series C n H 2n+1 .OH. 

Methyl alcohol . . CH 3 .OH. 

Ethyl « C 2 H 5 .OH. 

Propyl " • C 3 H 7 .OH. 

Butyl " C 4 H 9 .OH. 

Pentyl " C 5 H n .OH. 

Hexyl " C 6 H 13 .OH. 

Heptyl " C 7 H 13 .OH. 

Octyl " . C 8 H 17 .OH. 

Nonyl " C 9 H 19 .OH. 

Cetyl " C 16 H33.0H. 

Ceryl " C 27 H 55 .OH. 

Myricyl " 'QdH^.OH. 

2. Aldehydes. 

In general, it follows from what has been said concerning 
the properties of primary alcohols, that there should be an 
aldehyde corresponding to every primary alcohol. Many of these 
have been prepared. They resemble ordinary acetic aldehyde so 
closely that it is unnecessary to take them up individually. If 
we know the structure of the alcohol from which ««,n aldehyde is 
formed by oxidation, we also know the structure of the aldehyde. 

Besides the one method for the preparation of aldehydes 
which has been mentioned, viz., the oxidation of primary 
alcohols, there is one other which should be specially noticed. 
It consists in distilling a mixture of a formate and a salt of 
some other acid. Thus, when a mixture of an acetate and a 
formate is distilled, acetic aldehyde is formed as represented 
by the equation : — 



CHg.COOM 
H.COOM" 



= CH 3 .COH f-M 2 C0 3 

Aldehyde. 



FATTY ACIDS. 129 

This method has been used to a considerable extent in making 
the higher members of the series. 

Experiment 32. Mix about equal weights of dry calcium formate 
and dry calcium acetate. Distil from a small flask. Collect some of the 
distillate in water, and determine whether aldehyde is formed. 

3. Acids. 

Formic and acetic acids are the first two members of an 
homologous series of similar acids, generally called the fatty 
acids because several of them occur in large quantities in the 
natural fats. The names and formulas of some of the principal 
members are given in the following table. The reasons for 
representing the acids as compounds containing the carboxyl 
group, C0 2 H, have been given, and need not here be re- 
stated : — 

FATTY ACIDS. 
Series C n H 2n + 1 .C0 2 H, or C^H^O;,. 

Formic acid H.CO,H. 

Acetic "• CH3.CO0H. 

Propionic " C 2 H 5 .C0 2 H. 

« Butyric « C3H 7 .CO L ,II. 

Valeric " C 4 H 9 .C0 2 II. 

Caproicor j CR CQ 

Hexoic acids ( 

CEnanthylic or \ r . 

lleptoic acids ) 

^7 licm ; 1 c T ii,-.. con. 

Octoie acids ) 

Pelargonioor \ CH l; .CO : lI. 



/ 



Nonoic acids j 

Capric acid (yi u ,.CO,H 



130 DERIVATIVES OF THE PARAFFINS. 

Laurie acid CuH^.CC^H. 

Myristic " CUE*. CO»H. 

Palmitic " C 15 H 31 .C0 2 H. 

Margaric " C 16 H33.C0 2 H. 

Stearic " ........ C^H^.COsH. 

Arachidic " . C 19 H 39 .C0 2 H. 

Behenic " C 21 H43.C0 2 H. 

Hyenic " ........ C 24 H 49 .C0 2 H. 

Cerotic " C 26 H 53 .C0 2 H. 

Melissic " C M H M .CO,H. 

Although, as will be seen, a large number of fatty acids are 
known, most of them included in the list are at present merely 
curiosities, and need not be specially studied. Not more than 
six in addition to formic and acetic acids will require attention. 

Propionic acid, Propanic acid, CsHeC^^Hs-COaH).— 
Propionic acid is formed in small quantity (1) by the distil- 
lation of wood; (2) by the fermentation of various organic 
bodies, particularly calcium lactate and tartrate ; (3) by treat- 
ing ethyl cyanide (propio-nitrile) with caustic potash : — 

C 2 H 5 .CN -f KOH + H 2 = C 2 H 5 .C0 2 K +M 3 ; 

and (4) by oxidizing normal propyl alcohol. This last method 
is used on the large scale. 

Other methods for preparing it are the following : — 

(1) By reducing lactic acid with hydriodic acid. (This will 
be explained under the head of Lactic Acid, which see.) 

(2) By the action of carbon dioxide upon sodium ethyl : — 

C0 2 + NaC 2 H 5 = C 2 H 5 . C0 2 Na. 

It is a colorless liquid with a penetrating odor somewhat re- 
sembling that of acetic acid. It boils at 141°. (Compare with 
boiling-points of formic and acetic acids.) 



PROPIONIC ACID. 131 

It yields a large number of derivatives corresponding to those 
obtained from acetic acid. 

Note for Student. — What is propionyl chloride ? and how can it be 
prepared ? It is analogous to acetyl chloride. 

The simple substitution-products of propionic acid present 
an interesting and instructive case of isomerism. There are 
two chlor-propionic acids, two brom-propionic acids, etc. Those 
products which are obtained by direct treatment of propionic 
acid with substituting agents are called a-products, and the 
isomeric substances /^-products. Thus we have a-chlor-propionic 
and a-brom-propionic acid, made by treating propionic acid with 
chlorine and bromine ; and (3-chlor-propionic acid and /3-brom- 
propionic acid, made by indirect methods. The difference be- 
tween these two series of derivatives is due to different relations 
between the constituents. The usual method of representation 
indicates the possibility of the existence of two isomeric chlor- 
propionic acids, and of similar mono-substitution products of 
propionic acid. The acid is represented thus : — 

CH3.CH2.CO2H. 

Now, if chlorine should enter into the compound, as represented 
by the formula CH,,C1.CH 2 .C0 2 H, (1) we should have 0110 of 
the chlor-propionic acids ; while, if it should enter as indicated 
in the formula CH 3 .CHC1.C0 2 H, (2) we should have the iso- 
meric product. We have thus two chlor-propionic acids actu- 
ally known, and our theory gives us two formulas. How can 
we tell which of the formulas represents a-chlor-propionic acid, 
and which the /8-acid? Only by carefully studying- all the 
reactions and methods of formation of both compounds. The 
best evidence is furnished by a study of the lactic acids, which 
will be shown to be 1 mono-substitution products o( propionic 
acid. a-Chlor-propionic acid can be transformed into a lactic 
acid, the structure of which is represented by the formula 
CH 8 .CH(OH).COaH, and by replacing the hydroxy] o( this 



132 DERIVATIVES OF THE PARAFFINS. 

lactic acid by chlorine, a-chlor-propionic acid is formed. It 
therefore follows that formula (2) above given is that of a-chlor- 
propionic acid, and formula (1) that of /3-chlor-propionic acid. 
Further, any mono-substitution product of propionic acid that 
can be made directly from a-chlor-propionic acid, or converted 
directly into this acid, is an a-product, and has the general 

formula 

CH 3 .CHX.C0 2 H; 

and, similarly, the /^-products have the general formula 

CH 2 X.CH 2 .C0 2 H, 

in which X represents any univalent atom or group. 

Butyric acids, Butanic acids, C4H802(C3H7-CC>2H). 

Normal butyric acid, CH 3 . CH 2 .CH 2 .C0 2 H. When butter is 
boiled with caustic potash, the potassium salts of butyric acid 
and of some of the higher members of the series are found in 
the solution at the end of the operation. Butter, like other 
fats, belongs to the class of compounds known as ethereal 
salts ; and these, as we have seen, when boiled with the alka- 
lies, are decomposed, yielding alcohol and alkali salts of acids 
(saponification). In the case of butter and of nearly all other 
fats, the alcohol formed is glycerol. Butyric acid occurs also 
in many other fats besides butter. 

It is most readily made by fermentation of sugar by what is 
known as the butyric acid ferment. This ferment probably is 
contained in putrid cheese. Hence, to make the acid, sugar 
and tartaric acid are dissolved in water, and, after a time, cer- 
tain quantities of putrid cheese and sour milk are added, and 
also some powdered chalk. At first the sugar is converted into 
glucose : — 

C 12 H 22 O n + H 2 = 2 C 6 H 12 6 . 

Cane sugar. Glucose. 

The glucose breaks up, yielding lactic acid, C 3 H 6 3 : — 
CgH^Oe = 2 C 3 H 6 3 . 

Glucose, Lactic acid, 



VALERIC ACIDS. 13S 

And, finally, the lactic acid is converted into butyric acid : — 
2 C 3 H 6 3 = C 4 H 8 2 + 2 C0 2 + 4 H. 

Other methods for the preparation of butyric acid are : — 

(1) By oxidation of normal butyl alcohol ; and 

(2) By treating normal propyl cyanide, CH 3 .CH 2 .CH 2 CN, 
with caustic potash. 

The acidis a liquid having an acid, rancid odor, like that of 
rancid butter. It boils at 162°. (Compare with the preceding- 
acids.) Like the lower members of the series it mixes with 
water in all proportions. 

Ethyl butyrate, C 3 H 7 .C0 2 C 2 H 5 , has a pleasant odor resembling 
that of pineapples. It is used under the name of essence oj 
pineapples. 

/-ITT 

Isobutyric acid, Methyl-prop anic acid, qjj > CH.CO2H. 

— From the two propyl alcohols the two chlorides, propyl chlo- 
ride, CH 3 .CH 2 . CH 2 C1, and isopropyl chloride, CH 3 >CHC1, can 
be made, and from these the corresponding cyanides, — 

Propyl cyanide ...... CH 3 .CH 2 .CH 2 CN, 

CH 
and Isopropyl cyanide .... 3 > CHCN. 

CH 8 

By boiling with caustic potash, the former is converted into 
normal butyric acid, as stated above ; while the latter yields 

CH 
isobutyric acid, 3 >CH.CO.,II. This acid can be prepared 

CHq 

C1I 
also by oxidizing isobutyl alcohol, :! > Cll.CILOH. It is 

found in nature in the carob bean. 

Isobutyric acid is a liquid which boils at 154°. Its odor is 
less unpleasant than that of the normal acid. 

Valeric acids, C & H l0 O,(C,H.,.CO,H\ — Four carboxyl de- 
rivatives oi' the butanes are possible. Four acids of the 
formula (\ll„,0., are known. 



134 DERIVATIVES OF THE PARAFFINS. 

pTT 

Inactive or ordinary valeric acid, qJ > CH.CH 2 .C0 2 H. 

— This acid is made by oxidizing inactive amyl alcohol. It 
can also be made (and this reaction reveals the structure of 
the acid) by starting with isobutyl alcohol, 3 >CH.CH 2 OH, 

converting this first into the chloride and then into the cyanide, 

CH 
and, finally, transforming the cyanide, which is 3 > CH.CH 2 CN, 

into the acid. It occurs in valerian root, whence its name. It 
is an unpleasant smelling liquid, boiling at 174°. It requires 
thirty parts of water for solution. 

Amyl valerate, C 4 H 9 . C0 2 C 5 H n , has the odor of apples, and is 
used under the name of essence of apples. 



Active valeric acid, ^„4>CH.CH 2 .CH 3 . —This acid 



CH; 

C0 2 H 

is prepared by oxidation of active amyl alcohol. Although the 

alcohol turns the plane of polarization to the left, the acid 
turns it to the right. The alcohol is said to be Icevo-rotatory, 
and the acid dextro-rotatory. 



The higher acids of the series are, for the most part, found 
in various fats. They are difficultly soluble in water. The 
highest members are solids. The two best known, because 
occurring in largest quantity, are palmitic and stearic acids. 
These are contained in combination with the alcohol, glycerol, in 
all the common fats. The fats will be treated under the head 
of Glycerol. 

Palmitic acid, C15H31.CO2H, can be made by saponifying 
many fats, as palm oil, olive oil, and bay berry tallow. The 
last-named fat consists of about one-fifth part of palmitin, four- 
fifths being free palmitic acid and a little lauric acid and laurin. 

It crystallizes in needles which melt at 62.6°. 

Stearic acid, C17H35.CO2H, is the acid contained in that 
particular fat known as stearin. The so-called "stearin can- 



soaps. 135 

dies" consist of stearic acid mixed with palmitic acid and a 
little paraffin, and from them stearic acid can be separated in 
pnre form by long-continued fractional crystallization from 
ether and alcohol. 

It crystallizes from alcohol in needles or laminae which melt 
at 69.3°. 

Soaps — In speaking of the decompositions of ethereal salts 
by boiling with alkalies, it was stated that this process is 
called saponification because it is best exemplified in the manu- 
facture of soaps from fats. The fats are themselves rather 
complicated ethereal salts. When they are boiled with an 
alkali, as caustic soda, the alcohol is liberated, and the alkali 
salts of the acids are formed. These salts are the soaps. They 
are in solution after the process of saponification is completed, 
and can be separated by adding a solution of common salt, in 
which they are insoluble. 

Experiment 33. In an iron pot boil about 25s of lard with a 
solution of caustic soda for two hours. After cooling, add a strong 
solution of sodium chloride. The soap will separate and rise to the 
top of the solution, where it will finally solidify. Dissolve some of 
the soap thus obtained in water, and filter. Add hydrochloric acid, 
when the free fatty acids, mainly palmitic and stearic acids, will 
separate as solids, which will rise to the top. The hydrochloric acid 
simply decomposes the sodium palmitate and stearate, giving free 
palmitic and stearic acids and sodium chloride : — 

C 15 H ;il .C0 2 Na + IIC1 = C 15 H. u .CO.,H + NaCl, 

Sodium Palmitate. Palmitic Acid. 

and C n II !5 .C0 2 Na + HC1 = C 17 1L,.C(UI + NaCl. 

Sodium Stearate. Stearic Acid.. 



The remaining derivatives of the higher members of the 
paraffin scries include the ethers, ketones, ethereal salts. 
mercaptans, sulphur ethers, sulphonio acids, oyanidea and 
isoeyanides, cyanates and isocyanates, sulpho-cyanates and 



136 DERIVATIVES OF THE PARAFFINS. 

isosulpho-cyanates, substituted ammonias and analogous com- 
pounds, metal derivatives, and nitro-derivatives. 

A great many substances belonging to these classes, and 
containing residues of the higher hydrocarbons, have been pre- 
pared and studied ; but, in the main, they so closely resemble 
the simpler substances which have already been described that 
we should gain nothing by taking them up here individually. 
The student, however, is earnestly advised to apply the princi- 
ples discussed in the first part of the book to a few other cases. 
Thus, let him take propane and butane, and, not only write the 
formulas of the derivatives which can be obtained from them, 
but, above all, write the equations representing the action in- 
volved in their preparation, and the transformations of which 
they are capable. 

POLYACID ALCOHOLS AND POLYBASIC ACIDS. 

1. Di-acid Alcohols. 

The alcohols thus far treated of are of the simplest kind. 
They correspond to the simplest metallic hydroxides, as potas- 
sium hydroxide, KOH. Just as these simplest metallic hydrox- 
ides are called mon-acid bases, so the simplest alcohols are 
called mon-acid alcohols, 1 expressions which are suggested by 
the term mono-basic acid. But, as is well known, there are 
metallic hydroxides, like calcium hydroxide, Ca(OH) 2 , barium 
hydroxide, Ba(OH) 2 , etc., which contain two hydroxyls, and 
are hence known as di-acid bases; and so, too, there are di-acid 
alcohols which bear to the mon-acid alcohols the same relation 
that the di-acid bases bear to the mon-acid bases. Only one 
alcohol of this kind, derived from the paraffin hydrocarbons, is 
well known. 

Ethylene alcohol or glycol, Bthandiol, C2He02[C2H4 

(OH)2j Glycol is made by starting with ethylene, a hydro- 

1 The expression monatomic alcohols is used by some writers, but, as it is confusing, 
it is gradually giving way to the more rational expres'sion above used. 



ETHYLENE ALCOHOL. 137 

carbon of the formula C 2 H 4 . When this is brought together 
with bromine, the two unite directly, forming ethylene bromide, 
C 2 H 4 Br 2 . By replacing the two bromine atoms by hydroxyl, 
ethylene alcohol or glycol is formed. 

It is a colorless, inodorous, somewhat oily liquid, which boils 
at 197.5°. It has a sweetish taste, and is hence called glycol 
(from yAvKvs, sweet). Hence, further, the other alcohols of 
this series are also called glycols. 

The derivatives of ethylene alcohol are not as numerous as 
those of the better known members of the methyl alcohol series, 
but those which are known are of the same general character. 
The reactions of the alcohol are the same as those of the mon- 
acid alcohols, but it presents more possibilities. In most cases 
in which a mon-acid alcohol yields one derivative, ethylene 
alcohol yields two. Thus, with sodium, the two compounds, 

sodium glycol, C 2 H 4 < a ', and di-sodium glycol, C 2 H 4 < a , 

can be formed ; from these, by treating with ethyl iodide, the 

Of H 

two ethers/ elhyl-glycol ether, C 2 H 4 < 2 5 , and di-ethyl-gl ycol 

OH 

ether, C 2 H 4 < n 2 5 , are made. By treatment with hydro- 

CI 
chloric acid, the chloride, C 2 H 4 < , known as ethylene chlor- 

hydrine is formed ; and this, by treatment with phosphorus tri- 
chloride, can be converted into ethylene chloride, (\.II.,( L. etc. 
Its conduct towards acids is like that of a di-acid base. It 
forms neutral and alcoholic salts, of which the acetates may 
serve as examples. Thus we have the 



tut , , nu ^O.CjHsO 

Mono-acetate, C 2 II 4 < - ° , 



Oil 



and the Di-acetate, C,II 4 < OC - ,l ° ; 

oc\.ii,o 

the Conner still containing alcoholic hydroxyl and corresponding 
to a basic salt.; the Latter being a neutral compound. 



138 DERIVATIVES OF THE PARAFFINS. 

The formation of the diacetate is a step in one of the methods 
of preparing ethylene alcohol. This method consists in treating 
ethylene bromide with potassium acetate in alcoholic solution, 
separating the acetates of ethylene thus formed, and decom- 
posing these by means of barium hydroxide. The reactions 
involved are represented by the following equations : — 

nrr > Br KO.C 2 H 3 _ p tt O.C 2 H 3 9 ^^ ' 
C2H4< Br + KO.C 2 H 3 ~ ° Mi< O.C 2 H 3 + 2 KBr > 

and C 2 H 4 < qJJJ 3 q +Ba < °[j = C 2 H 4 < g| +Ba(C 2 H 8 2 ) 2 . 

The alcohol can also be made by treating ethylene bromide 
with potassium carbonate : — 

C 2 H 4 < ^ r + K° >CO + H 2 = C 2 H 4 < ^ + 2KBr +C0 2 ; 
Br KO OH 

and by treating ethylene bromide with silver oxide : — 
C 2 H 4 < ^ + Ag 2 + H 2 = C 2 H 4 < ^ + 2 AgBr. 

These methods of formation show clearly what ethylene alcohol is. 
When acetyl chloride acts upon the alcohol at ordinary tem- 

OC H O 

perature, the product has the formula C 2 H 4 < 2 3 . This is 

>^1 
also formed by the action of hydrochloric acid gas on the diace- 
tate. It seems probable, therefore, that the action of acetyl 
chloride is to be represented by two equations ; thus : — 

C 2 H 4 < °JJ + 2 C 2 H 3 0C1 = C 2 H 4 < °C 2 H 3 + 2 HC1 . 

and C 2 H 4 < °£ 2 ^° + HC1 = C 2 H 4 < °°* U *° + C 2 H 4 2 . 

There are two ways in which the structure of a compound 

of the formula C 2 H 4 (OH) 2 can be represented. They are, — 

CH 2 (OH) 
(1) I , in which each hydroxyl is represented in combi- 

CH 2 (OH) CH(OH) 2 

nation with a different carbon atom ; and (2) I , in which 

v y CH 3 

both hydroxyls are represented in combination with the same 



ETHYLENE ALCOHOL. 139 

carbon atom. The question at once suggests itself, to which of 
these formulas does ethylene alcohol correspond? To answer 
this question, we must recall what was said regarding the two 
dichlor-ethanes, known as ethylene chloride and ethylidene chloride. 
The former of these corresponds to the formula CH 2 C1.CH 2 C1, 
while the latter, which is formed from aldehyde b}* replacing the 
carbonyl oxygen by two chlorine atoms, is represented by the 
formula CHC1 2 .CH 3 . When the chlorine atoms of ethylene 
chloride are replaced by hydroxyl, ethylene alcohol is produced. 

CH 2 (OH) 
Hence, the alcohol has the formula I , or each of the 

CH 2 (OH) 

hydroxyls is in combination with a different carbon atom. 

All attempts to make the isomeric di-acid alcohol correspond- 
ing to ethylidene chloride, and having both hydroxyls in combi- 
nation with the same carbon atom, as represented in the formula 

CH(OH 2 ) 

I , have failed. Instead of getting ethylidene alcohol. 

CH 3 

aldehyde is generally obtained. Aldehyde is ethylidene alcohol 

minus water : — 

CH(OH) 2 CHO 

I = I +H 2 0. 

CH 3 CH 3 

It is believed that one carbon atom cannot, under ordinary 
circumstances, hold in combination more than one hydroxyl 
group. If this is true, then ethylidene alcohol cannot be pre- 
pared any more than the hypothetical carbonic acid, CO < ( , 

can be. So, too, the simplest di-acid alcohol conceivable, 
viz., methylene alcohol, CH 2 (OH) 2 , cannot exist, but would 
break up, if formed at all, into water and formic aldehyde : — 

CII 2 (OII),,= HjO + H.CTIO. 

(See discussion regarding the transformation of alcohol into 
aldehyde, pp. 64-66.) 



140 DERIVATIVES OF THE PARAFFINS. 

Ethyl alcohol, as was pointed out, may be regarded either as 
ethane in which one hydrogen is replaced by hydroxyl, or as 
water in which one hydrogen is replaced by the radical C 2 H 5 , or 
ethyl. Ethyl, like ail the radicals contained in the mon-acid 
alcohols, is univalent. It is ethane less one atom of hydrogen, 
just as methyl is methane less one atom of hydrogen. Each 
has the power of uniting with one atom of hydrogen, or another 
univalent element, or of taking the place of one atom of 
hydrogen. 

If we take away two atoms of hydrogen from methane and 
ethane, we have left the residues or radicals CH 2 and C 2 H 4 . 
These can unite with two atoms of hydrogen, or take the place 
of two atoms of hydrogen, and they are hence called bivalent 
radicals. 

Just as ethylene alcohol may be regarded as ethane in which 
two Irydrogen atoms are replaced by hydroxyls, so it may be 
regarded as water in which the bivalent radical ethylene re- 
places two hydrogens belonging to two different molecules of 
water : — 

°<H 0< H 

0<H °<H H< 

Two molecules water. Ethylene alcohol. 



The higher members of the series of di-acid alcohols will not 
be considered here. 

2. Dibasic Acids. 

Just as there are di-acid alcohols derived from the paraffins, 
so there are dibasic acids which may also be regarded as deriva- 
tives of the paraffins. We have seen that the simplest acids, 
the monobasic fatty acids, are closely related to formic and 
carbonic acids ; that they may be regarded as derived from the 
latter by replacement of a hydroxyl by a radical, or as derived 



DIBASIC ACIDS. 141 

from the paraffins by the introduction of the group carboxyl, 
C0 2 H. The conditions existing in this group are essential to 
the acid properties. If two carboxyls are introduced into marsh 
gas, a substance of the formula CH 2 (C0 2 H) 2 is formed, and 
this is a dibasic acid. It contains two acid hydrogens, and 
is capable of forming two series of salts, the acid and neutral 
salts, like other dibasic acids. It may be regarded also as 
derived from two molecules of carbonic acid by the replacement 
of two hydroxyls by the bivalent radical CH 2 : — 

CO<5^ m .OH 



OH CO< 



CH 2 



co< oS C ° <0H 

Two molecules carbonic acid. Dibasic acid. 

The general methods of preparation available for the building 
up of the series of dibasic acids are modifications of those used 
\n making the monobasic acids. They are : — 

1. Oxidation of di-acid primary alcohols. Just as a mon- 
acid primary alcohol, R.CH 2 OH, yields by oxidation a mono- 
basic acid, so a cli-acid primary alcohol, R"(CH 2 OH) 2 , yields a 
dibasic acid,JR/'(C0 2 H> 2 . 

2. Treatment of the dicyanides, R"(CN) 2 , with caustic alkalies. 

3. Oxidation of the hydroxy -acids or alcohol acids. These 
are compounds which are at the same time alcohol and acid ; 
as, for example, hydroxy-acetic acid, which is acetic acid in 
which one of the hydrogen atoms of the hydrocarbon residue, 
methyl, has been replaced by hvdroxvl, as represented in the 

cii.on 

formula, I . When this is oxidized, (he alcoholic portion, 

CO, 1 1 

CH 2 OH, is converted into carboxyl, and a dibasic acid is formed. 

4. From the cyanogen derivatives o\' (he monobasic acids. 

such as cyan-acetic acid, en, < :L , by the transformation of 

the cyanogen group into carboxyl. 



142 DERIVATIVES OF THE PARAFFINS. 

DIBASIC ACIDS, C n H 2n _ 2 4 . 

Oxalic acid (C0 2 H) 2 . 

< Malonic " CH 2 (C0 2 H) 2 . 

/ Succinic " C 2 H 4 (C0 2 H) 2 . 

'pPyrotartaric " C 3 H 6 (C0 2 H) 2 . 

Adipic « ...... . C 4 H 8 (C0 2 H) 2 . 

Pimelic " C 5 H 10 (CO 2 H) 2 . 

Suberic " . C 6 H 12 (C0 2 H) 2 . 

Azelaic " C 7 H 14 (C0 2 H) 2 . 

Sebacic " . . C 8 H 16 (C0 2 H) 2 . 

Brassylic " C 9 H 18 (C0 2 H) 2 . 

Roccellic " C 15 H 30 (CO 2 H) 2 . 



Of the many acids included in this list only four or five can 
be said to be well known. We may confine our attention to the 
first four members. 

Oxalic acid, 2 H2O 4 [(0O 2 H)2]. — In one sense, according to 
the accepted definition, oxalic acid is not a member of the series 
with which we are dealing, as it is not derived from a hydro- 
carbon by replacement of hydrogen by carboxyl ; nor is it 
derived from two molecules of carbonic acid by replacement of 
two hydroxyls by a bivalent radical. Still it is in other respects 
so closely allied to the members of the series, and has so many 
things in common with the other members, that it would be a 
mere act of pedantr}^ to consider it in any other connection. 

Oxalic acid occurs very widely distributed in Nature ; as in 
certain plants of the oxalis varieties, in the form of the acid 
potassium salt ; as calcium salt in many plants ; in urinary 
calculi ; and as the ammonium salt in guano. 

It is formed by the action of nitric acid upon many organic 



OXALIC ACID. 143 

substances, particularly the different varieties of sugar and the 
so-called carbohydrates, such as starch, cellulose, etc. 

Experiment 34. In a good-sized flask pour half a litre of ordinary 
concentrated nitric acid (of specific gravity 1.245) upon 50& of sugar. 
Heat gently until the reaction begins. Then withdraw the flame, when 
the oxidation will proceed with some violence, and accompanied by 
a copious evolution of red fumes. When the action has ceased, 
evaporate the liquid to one-sixth the original volume, and let it 
cool, when oxalic acid will crystallize out. Recrystallize from water 
the acid thus obtained, and with the pure substance perform such ex- 
periments as will exhibit its properties. For example, (1) Heat a 
specimen at 100°, and notice loss of water; (2) Heat some in a small 
flask with sulphuric acid, and prove that both oxides of carbon are 
formed. 

On the large scale, oxalic acid is made by heating wood 
shavings or saw-dust with caustic potash and caustic soda to 
240° to 250°. The mass is extracted with water, and the solu- 
tion evaporated to crystallization, when sodium oxalate is de- 
posited. 

Other methods, which are interesting from a purely scientific 
point of view, are the following : — 

1 . The spontaneous transformation of an aqueous solution of 
cyanogen : — 

CN C0 2 H 

| +4H 2 = | + 2NH 3 ; 

CN C0 2 H 

CN CO^NH,) 

or, really, | + 4 II 2 = I 

CN COoCNHj 

2. Treatment of carbon dioxide with sodium: — 

2 C0 2 + 2 Na = CAN*. 

3. Heating sodium formate : — 

2H.COjNa = CANaj + 2H. 
Oxalic acid crystallizes from water in monoclinic prisms con 



144 DEEIVATIVES OF THE PARAFFINS. 

taining two molecules of water (CaH^O^ + 2 H 2 0) . It loses 
this water at 100°. It sublimes without decomposition at 150° 
to 160°, but, if heated higher, it breaks up into carbon monox- 
ide, carbon dioxide, and formic acid: — 

2 C 2 H 2 4 = 2 C0 2 + CO + HC0 2 H + H 2 0. 

Sulphuric acid decomposes it into carbon monoxide, carbon 
dioxide, and water. Heated with glycerol to 100°, carbon 
dioxide and formic acid are formed (see Formic Acid) : — 

C 2 H 2 4 = C0 2 + H.C0 2 H. 

It is an excellent reducing agent, and is used as a standardizer 
in preparing solutions of potassium permanganate. 

Experiment 35. Try the action of a solution of potassium per- 
manganate on a solution of oxalic acid. Why is it best to have tfche 
solution of the permanganate acid? 

Oxalic acid is an active poison. It is used in calico printing. 

Salts of oxalic acid. Like all dibasic acids, oxalic acid forms 
acid and neutral salts with metals. All the salts are insoluble 
except those containing the alkalies. Among those most com- 
mon are the acid potassium salt, C 2 4 HK, which is found in the 
sorrels or plants of the oxalis variet} 7 ; the ammonium salt, 
C 2 4 (NH 4 ) 2 , of which some urinary calculi are formed; and 
calcium oxalate, C 2 4 Ca, which, being insoluble in water and 
acetic acid, is used as a means of detecting calcium in the pres- 
ence of magnesium, and of estimating calcium and oxalic acid. 

Malonic acid, C 3 H,0 4 [= CH 2 (C0 2 H),].— This acid was first 
made by oxidation of malic acid (which see), and 'is hence 
called malonic acid. It can best be made by starting with 
acetic acid. The necessary steps are : (1) making chlor-acetic 
acid ; (2) transforming chlor-acetic acid into cyan-acetic acid ; 
(3) heating cyan-acetic acid with an alkali. 

Note for Student. — Write the equations representing the three 
steps mentioned. 



SUCCINIC ACIDS. 145 

It is a solid which crystallizes in laminae. It breaks up at a 
temperature above 132°, which is its melting-point, into carbon 
dioxide and acetic acid : — 

CH * < ™ 5 = CH3.COJH + C0 2 . 
OU 2 ri 

Note for Student. — What simple method for the preparation of 
marsh gas and other paraffins is this reaction analogous to ? 

Succinic acids, C4H 6 04[ = C 2 H4(C02H)2].— Regarding these 
acids as derived from ethane by substituting two carboxyls for 
two hydrogens, it is clear that there may be two, one corre- 
sponding to ethylene chloride and another corresponding to 
ethylidene chloride. Two are actually known. One is the 
well-known succinic acid; the other is called isosuccinic acid. 

CH,.CO,H 
Succinic acid, Ethylene succinic acid, I . — 

CH 2 .C0 2 H 
This acid occurs in amber (hence its name, from Lat. succinum, 
amber) ; in some varieties of lignite ; in many plants ; aud in 
the animal organism, as in the urine of the horse, goat, and 
rabbit. 

It is formed under many circumstances, especially by oxida- 
tion of fats with nitric acid, by fermentation of calcium malate, 
and, in small quantity, in the alcoholic fermentation of sugar. 
Among the methods for its preparation are : — 

(1L.CN 

1. Treatment of ethylene cyanide, | , with a caustic 
alkali:— CEL.CN 

CHoCN CH...CO..K 

I -f- 2 KOII + 2 11,0 = I +2 NH S . 

CH 2 CN ClI,.CO,K 

2. Similarly, by treatment of /8-cyan-propionic acid with an 
alkali. (What is /8-cyan-propionic acid?) 

3. Reduction of tartaric and malic acids bv means of 



146 DERIVATIVES OF THE PARAFFINS. 

hydriodic acid. These well-known acids will be shown to be 
closely related to succinic acid, and the reaction here mentioned 
will be explained. The methods actually used in the prepara- 
tion of succinic acid are : (1) the distillation of amber, and 
(2) the fermentation of calcium malate. 

The acid crystallizes in monoclinic prisms, which melt at 
185° (try it). It boils at 235°, at the same time giving off 
water, and being converted into the anhydride: — 

Succinic anhydride is a solid substance that crystallizes well 
from chloroform. It is converted into succinic acid by boiling 
with water. When boiled with alcohols it yields the cbrre- 
sponding ester acids. For example, with ordinary alcohol 
monoethyl succinate is formed. 

C 2 H 4 < g> > o + C,H s OH = C 2 H 4 < £°°^ H5 . 

Among the salts basic ferric succinate, C 4 H 4 04.Fe(OH), is of 
special interest, as it is entirely insoluble in water, and can 
therefore be used for the purpose of separating iron and alu- 
minium from manganese, zinc, nickel, and cobalt quantitatively. 

Experiment 36. Make a neutral solution of ammonium succinate 
by neutralizing an aqueous solution of the acid, and boiling off all 
excess of ammonia. Add some of this solution to a solution known to 
contain manganese and iron in the ferric state. A brown-red precipitate 
will be formed. Filter and wash, and examine the filtrate for iron. 

CH(C0 2 H) 2 
Isosuccinic acid, Bthylidene succinic acid, I 

CH 3 

This acid is made by treating a-cyan-propionic acid with an 
alkali. (What is a-cyan-propionic acid ? ) 

Isosuccinic acid forms crystals which melt at 130°. Heated 
above its melting-point it breaks up into propionic acid and 
carbon dioxide: — 



GLYCEROL. 147 

CH(C0 2 H) 2 CH 2 .C0 2 H 

I = I + co 2 . 

CH 3 CH 3 

Isosuccinic acid. ' Propionic acid. 

Note for Student. — Notice carefully the difference between the two 
succinic acids, as shown by their conduct when heated. What is the 
difference ? 

Acids of the formula C 5 H 8 4 [ = CsHeCCCKH^].— Four 
acids of the formula C 5 H 8 4 are known, only one of which, 
however, need be mentioned here. This is, — 

CH3CHCO2H 
Pyrotartaric acid, . — As the name indi- 

CH2.CO2H 

cates, this acid may be made by dry distillation of tartaric acid. 

Tri-acid Alcohols. 

The existence of mon-acid alcohols corresponding to the mon- 
acid bases, like potassium hydroxide, and of di-acid alcohols 
corresponding to the di-acid bases, like calcium hydroxide, sug- 
gests the possible existence of tri-acid alcohols corresponding to 
tri-acid bases, like ferric hydroxide. There is only one alcohol 
of this kind derived from the paraffin hydrocarbons that is at 
all well known. This is the common substance glycerin or 
glycerol. 

Glycerol, Glycerin, Propantriol, C;;HsO;;. — As has been 
stated repeatedly, glycerol occurs very widely distributed as the 
alcoholic or basic constituent of the fats. The acids with which 
it is in combination are mostly members of the tatty acid series. 
though one, viz., oleic acid, which is found frequently, is a mem- 
ber of another series. Besides oleic acid the two acids most 
frequently met with in fats are palmitic and stearic acids. 
When a fat is saponified with caustic potash, it yields free 
glycerol and the potassium salts of the acids. The reactions in 
the case of the glycerol compounds o{^ palmitic and stearic acids 
are these : — 



148 DERIVATIVES OF THE PARAFFINS. 

Formation. 
C 3 H 5 (OH) 3 + 3 HO . OC . C 15 H 31 = C 3 H 5 (0 . OC . C 15 H 31 ) 3 + 3 H 2 0. 

Glycerol. Palmitic acid. Glycerol tri-palinitate, 

or Palmitin. 

C 3 H 5 (OH) 3 + 3 HO . OC . CJ3* = C 3 H 5 (0 . OC . C^H*), + 3 H 2 0. 

Glycerol. Stearic acid. Glycerol tri-stearate, 

or Stearin. 

Saponification. 
C 3 H 5 (0 . OC . C 15 H 31 ) 3 + 3 KOH = C 3 H 5 (OH) 3 + 3 C 15 H 31 . C0 2 K. 

Palmitin. Glycerol. Potassium palmitate. 

C 3 H 5 (0 . OC . C^H^a + 3 KOH = C 3 H 5 (OH) 3 + 3 C 17 H 35 . C0 2 K. 

Stearin. Glycerol. Potassium stearate. 

The fats are also decomposed by superheated steam, yielding 
free glycerol and the free acids, and this method is used on the 
large scale, a little lime being added to facilitate the process. 
Lead oxide decomposes fats yielding a mixture of glycerol and 
the lead salts of the acids. The mixture is known in medicine 
as " lead plaster." 

Glycerol is formed in small quantity by the alcoholic fermen- 
tation of sugar. 

It has been made synthetically from propylene chloride, 
C 3 H 6 C1 2 . The necessary steps are : (1) treatment with chlorine, 
giving C 3 H 5 C1 3 ; (2) treatment of the tri-chlorine derivative with 
water, thus replacing the three chlorine atoms by hydroxy!. 

Glycerol is a thick colorless liquid, with a sweetish taste 
(compare with glycol). It mixes with alcohol and water in all 
proportions but is insoluble in ether. It attracts moisture from 
the air. At low temperatures it solidifies, forming deliquescent 
crystals which melt at 17°. Pure glycerol boils at 290° without 
decomposition. If salts are present it undergoes decomposition 
at the boiling temperature. Under diminished pressure it can 
be distilled ; but, if heated to its boiling-point under the 
ordinary atmospheric pressure, it undergoes decomposition. 
It is volatile with water vapor. 

Glycerol is used to some extent in medicine, but its chief use 
is in the manufacture of nitro-qlvcerin. 



GLYCERIN. 149 

Experiment 37. Heat a little commercial glycerol in a dry vessel, 
and try to boil it. What evidence have you that it undergoes decom- 
position ? Put 20 cc to 30 cc glycerol in 400 cc to 500 cc water in a flask ; con- 
nect with a condenser, and boil. Prove that glycerol passes over with 
the water vapor. 

The reactions of glycerol all clearly lead to the conclusion 
that it is a tri-acid alcohol. 

(1) The three hydroxyl groups can be replaced successively 
by chlorine, giving the compounds, — 

Chlorhydrin, C 3 H 5 ■! /qtt\ ; 

{ CI 
Dichlorhydrin, C 3 H 5 -J ^X ; 

and Trichlorhydrin, C 3 H 5 C1 3 , 

which last compound is propane in which three hydrogen atoms 

are replaced by chlorine, or trichlorpropane. 

(2) It forms three classes of ethereal salts containing one, 
two, and three acid residues respectively. For example, with 
acetic anhydride these reactions take place : — 



(OH 

OH + (C 2 H 3 0) 2 =C 3 H 5 . 
(OH (OH 



C 3 H 5 1 OH + (C 2 H 3 0) 2 = C 3 H 5 ■> OH + CoH 4 



( OH t OC,H 3 

2. C 3 H 5 1 OH + 2 (C 2 H 3 0) 2 = C 8 H 6 i OC 2 H 3 + 2 C 2 H 4 2 - 

(OH (OH 

( OH t OC 2 H 3 

3. C 3 IlJ OH + 3 (C 2 H 3 0) 2 = Cy I, OC 2 H 3 + 3 C 2 H 4 O a . 

(oh (or. ,ii,o 

In regard to the relations of the hydroxyl groups to the parts 
of the radical C 3 H 5 , we have very little experimental evidence, 

though it appears highly probable that each hydroxy I is in 
combination with a different carbon atom as represented in the 
CH 8 OH 

formula CI 10 II . 
I 
C 11,011 



150 DERIVATIVES OF THE PARAFFINS. 

In the first place, we have seen above that compounds con- 
taining two hydroxyls in combination with the same carbon 
are not readily formed, if they are formed at all, and we have 
had some reason for concluding that this kind of combination 
is impossible. It would follow from this that the simplest tri- 
acid alcohol must contain at least three atoms of carbon, just 
as the simplest di-acid alcohol must contain at least two atoms 
of carbon. We have seen that the simplest tri-acid alcohol 
known does contain three atoms of carbon. 

CH 2 OH 

Further, if the formula of glycerol is CHOH , it contains two 

CH 2 OH 
primary alcohol groups, CH 2 OH, and we have seen that this 
group is converted into carboxyl under the influence of oxidiz- 
ing agents. Therefore, we should expect by oxidizing glycerol 

C0 2 H *C0 2 H 

I I 

to get products of the formulas, CHOH , and CHOH. Such prod- 

i CH 2 OH C0 2 H 

ucts actually are obtained, the first being glyceric acid (which 
see), and the second tartronic acid (which see). 

Just as ethyl alcohol is regarded as water in which one 

C H ) 

hydrogen is replaced by the univalent radical C 2 H 5 , as 2 5 j- ; 

and glycol is regarded as water in which two hydrogen atoms 
of two molecules of water are replaced by the bivalent radical 

H >0 

C 2 H 4 , as C 2 H 4 ; so also glycerol may be regarded as water 

H >U 
in which three hydrogen atoms of three molecules are replaced 
by the trivalent radical C 3 H 5 , thus : — 



H.OH 


rOH 


H.OH 


c s hJoh, 


H.OH 


(.OH 


Three molecules water. 


Glycerol. 



BUTTER. 151 

Ethereal salts or esters of glycerol. — Among the im- 
portant esters of glycerol are the nitrates. Two of these 

f O.N0 2 
are known ; viz., the mono-nitrate, C 3 H 5 { OH , and the tri- 

[OH 
nitrate, C 3 H 5 (ON0 2 ) 3 , the latter being the chief constituent of 
nitro-glycerin. Nitro-glycerin is prepared by treating glycerol 
with a mixture of concentrated sulphuric and nitric acids. It 
is a pale yellow oil which is insoluble in water. At —20° it 
crystallizes in long needles. It explodes very violently by 
concussion. It can be burned in an open vessel, but if heated 
quickly it explodes. It also explodes by percussion. Dyna- 
mite is infusorial earth impregnated with nitro-glycerin. Mixed 
with nitrocellulose (which see) it forms smokeless powder. It 
is the active constituent of other explosives. 

When treated with a caustic alkali, nitro-glycerin is saponi- 
fied, yielding glycerol and a nitrate. This shows that it is an 
ester of nitric acid, and not a nitro-com pound. 

Fats. — The relation of the fats to glycerol has already 
been stated. Most fats are mixtures of the three neutral 
esters which glycerol forms with palmitic, stearic, and oleic 
acids, and which are known by the names palmitin, stearin, and 
ole'in. Olein is liquid, and the other two fats are solids, stearin 
having the higher melting-point. Therefore, the larger the 
proportion of olein contained in a fat, the softer it is, while 
the greater the proportion of stearin, the higher its melting- 
point. Among the fats which are particularly rich in stearin 
may be mentioned mutton tallow, beef tallow, and lard. Human 
fat and palm oil are particularly rich in palmitin. Sperm oil 
and cod-liver oil are rich in olein. Fats occur very widely dis- 
tributed in nature, both in plants ami animals. They are oi' 
the highest importance from the physiological point oi' view. 
forming one of the three great classes oi' food-stuffs. 

Butter consists of ethereal salts of glycerol and the follow- 
ing acids: myristic, palmitic, and stearic acids, which are not 



152 DERIVATIVES OF THE PARAFFINS. 

volatile, and butyric, caproic, caprylic, and capric acids, which 
are volatile with water vapors. All the acids mentioned are 
members of the fatty acid series. Some of these acids are sol- 
uble and some are insoluble in water. The percentage of in- 
soluable fatty acids contained in butter has been found to be 
88 per cent. As the proportion of insoluble fatty acids con- 
tained in artificial butters, such as the so-called oleo-margarin, 
is greater than that contained in butter, it is not a difficult 
matter to distinguish between the two by determining the 
amount of these acids contained in them. 

Tri-basic Acids. 
Tri-carballylic acid, CsHsCCOsEQs. — This acid can be 
made from trichlorhydrin, C 3 H 5 C1 3 (which see), by replacing 
the chlorine by cyanogen, and heating with an alkali the tri- 
cyanhydrin thus obtained. It can be made also by treating 
aconitic acid (which see) with nascent hydrogen. It crystal- 
lizes from water in rhombic prisms which melt at 157° to 158°. 

Tetr-acid Alcohols. 
Brythrol, Brythrite, C4H10O4 = C 4 H 6 (OH)4]. — This sub- 
stance occurs in one of the algae (Protococcus vulgaris) and in 
several lichens. It crystallizes from water in quadratic prisms. 
It has a very sweet taste. The fact that the simplest tetr-acid 
alcohol contains four atoms of carbon should be specially noted. 



There is no well known tetra-basic acid derived from the 
hydrocarbons of the paraffin series. 



Pext-acid Alcohols. 



One pent-acid alcohol occurs in nature in Adonis vernalis, 
and it is hence called adonite. It is also formed by reduction 
of rhamnose (which see). 

By reduction of xylose (which see) a pent-acid alcohol, called 
xylite, is formed ; and by reduction of arabinose (which see) an- 
other called arabite is formed. 



HEX-ACID ALCOHOLS. 153 

All the above named alcohols have the formula C 5 H 12 5 [ = 
C 5 H 7 (OH) 5 ]. There are three modifications of arabite — two 
optically active, and one inactive. There is still another pent- 
acid alcohol known as rhamnite, formed by reduction of rham- 
nose (which see). This has the composition represented by 
the formula C 6 H 14 5 [ = CH 3 .C 5 H 6 (OH) 5 ]. 



Two pentabasic acids have been made, but they are of no 
special importance. 

Hex-acid Alcohols. 

There are several hex-acid alcohols known. Most of them 
are derived from hexane, and have the composition represented 
by the formula C 6 H 8 (OH) 6 . It will be noticed that these hex- 
acid alcohols contain six carbon atoms each. 

Mannitol, Mannite, CeHsCOEQe. — Mannite is widely dis- 
tributed in the vegetable kingdom. It occurs most abundantly 
in manna, 1 which is the partly dried sap of the manna-ash 
(Fraxinus ornus). It is obtained from incisions in the bark 
of the tree. 

Mannite is formed in the lactic acid fermentation of sugar. 
It is formed also by the action of nascent hydrogen on fructose 
and mannose. It crystallizes in needles, or rhombic prisms, 
easily soluble in water and in alcohol. It has a sweet taste. 

Nitric acid converts mannite into rnanno-saccharic add 
(which see). When boiled with concentrated hydriodic acid, 
it is converted into secondary liexvl iodide, C 6 H 13 I. 

Mannite hexa-nitrate (nitro-mannite\ CV.Hs^O NO \,. is 
formed by treating mannite with a mixture of concentrated 
sulphuric and nitric acids. It is a solid substance and is Yen- 
explosive. (Analogy with uitro-glycerin.) 

1 The manna of the Scriptures was obtained from the branches o( ^bmrnartoo 
11 contained no mannite, bul a Bubstanoe of similar properties, 



154 DERIVATIVES OF THE PARAFFINS. 

Mannite hex-acetate, CeHsCO^HsOe, is formed by treat- 
ing mannite with, acetic anhydride. Its formation, as well as 
that of the hexa-nitrate, shows that mannite is a hex-acid alco- 
hol. Tlie number of acetyl groups that enter into a compound 
when it is treated ivith acetic anhydride shows how many hydroxyl 
groups are in the compound. 

There are three varieties of mannite — the ordinary, known as 
dextro-mannite, and, further, levo-mannite, and inactive mannite. 

Dulcite, CeHsCOHX — This occurs in a kind of manna 
obtained from Madagascar, the source of which, however, is 
unknown. It is formed by treating sugar of milk or galactose 
with nascent hydrogen (compare with mannite in this respect). 

Nitric acid oxidizes dulcite, forming mucic acid (which see), 
isomeric with manno-saccharic acid, which is formed from 
mannite. Like mannite, when boiled with hydriodic acid it 
yields secondary hexyl iodide, C 6 H 13 I. 

Sorbite, CeHsCOH^ Ordinary sorbite occurs in the berries 

of the mountain ash, and in many other fruits, as plums, cher- 
ries, apples, etc. It is formed by reduction of glucose, and also 
together with mannite by the reduction of fructose. This 
variety is known as dextro-sorbite, because it is formed from 
glucose, which is dextro-rotatory. Levo-sorbite is also known, 
having been obtained by the reduction of levo-gulose. 



There are no hexa-basic acids known belonging to this series. 



Hept-acid Alcohols, etc 

Perseite, CtHoCOH)?, occurs in the fruit and leaves of 
Laurus persea, and has been made artificially from dextro- 
mannose, by treating it with hydrocyanic acid, converting the 
nitril thus formed into the corresponding acid, and reducing 
this acid. It is also called dextro-mannoheptite. By similar 
reactions an oct-acid and a non-acid alcohol have been made 
from glucose, 




CHAPTER X. 

MIXED COMPOUNDS. -DERIVATIVES OP 
THE PARAFFINS. 

Under this head are included compounds that belong at the 
same time to two or more of the chief classes already studied. 
Thus, there are substances which are at the same time alcohols 
and acids. There are others which are at the same time alco- 
hols and aldehydes, alcohols and ketones, acids and ketones, 
etc. Fortunately, for our purpose, the number of compounds 
of this kind actually known is comparatively small, though 
among them are many of the most important natural com- 
pounds of carbon. The first class that presents itself is that 
of the alcohol acids or acid alcohols; that is, substances that 
combine within themselves the properties of both alcohol and 
acid. They are commonly called oxy-acids or hydroxy-acids. 

Hydkoxy-acids, C n H 2u 3 . 

These acids may be regarded either as monobasic acids into 
which one alcoholic hydroxyl has been introduced, or as mon- 
acid alcohols into which one carboxvl has been introduced. As 
their acid properties are more prominent than the alcoholic 
properties, they are commonly referred to the acids. Running 
parallel, then, to the series o( fatty acids, wo may look tor a 
series of hydroxy-acids, each ol' which differs from the corre- 
sponding fatty acid by one atom oi' oxygen, or by containing one 
hydroxyl in the place of one hydrogen, thus: — 



156 DERIVATIVES OF THE PARAFFINS. 





Fatty acid6. 


Hydroxy -acids. 


Formic acid . 


H.C0 2 H 


HO.C0 2 H. 


Acetic acid . 


. CH 3 .C0 2 H 


CH2< C0 2 H 


Propionic acid . 


(^2^-5 • v^ v-^-*-*- 


CA <C0 2 H 

etc. 




etc. 



The first member of the series, which by analogy would be 
called hydroxy -formic acid, is nothing but the ordinary hypo- 
thetical carbonic acid. Although its relation to formic acid is 
the same as that of the next member of the series to acetic 
acid, it certainly has no properties in common with the alcohols ; 
but, owing to its peculiar structure, it is a dibasic acid which 
the other members of the series are not. Nevertheless, it may 
be referred to here for the sake of a few of its derivatives, 
which are somewhat allied to those of the hydroxy-acids proper. 

Carbonic acid, H 2 Co/cO < ^Y — It is believed that 

this body exists in solutions of carbon dioxide in water. All 
that is known about it is that it is a feeble dibasic acid, and 
breaks up into water and carbon dioxide whenever it is set free 
from its salts. We have seen that this instability is generally 
met with in compounds containing two hydroxyls in combina- 
tion with one carbon atom. 

Among the derivatives of carbonic acid which may be 
mentioned at this time are the ethereal salts. These may be 
made : — 

1. By treating silver carbonate, CO<^ A f> with the iodides 
of alcohol radicals ; as, for example, — 

C0< nf g + 2 C ^ J = CO <^u + 2 A S L 

UAg UU2H5 

2. By treating the alcohols with carbonyl chloride, COCl 2 :— * 

COCl 2 + 2 C 2 H 5 OH = CO(OC 2 H 5 ) 2 + 2 HC1. 



ETHYL CHLOR-CARBONATE. 157 

Ethyl chlor-carbonate, OC<T~ — This compound 

OO2XI5 

is made by treating alcohol with carbonyl chloride : — 

COCl 2 + C 2 H 5 OH = OC<^ ^ + HC1. 

O0 2 rl 5 

It may be regarded as the ethyl ester of mono-chlor-formic 
acid, Cl.COOH; and, properly speaking, should be called ethyl 
chlor-formate. 

Carbon disulphide acts very much like carbon dioxide towards 
alkalies and alcohols, and thus a number of ether acids and 
ethereal salts containing sulphur can be made. Thus, when 
carbon disulphide is added to a solution of caustic potash in 

OP H 

alcohol, a potassium salt of the formula SC < sr 2 5 is formed. 

This is called potassium xanthogenate. Free xanthogenic acid 
is very unstable, breaking up into alcohol and carbon disulphide. 
The formation of the salt is represented by the following equa- 
tion : — 

CS 2 + KOH + aH 5 OH = SC<^ 2H5 + HX). 

A similar salt made from ordinary amyl alcohol has been used 
for the purpose of destroying phylloxera, the insect, which is so 
destructive to grape-vines, particularly in the wine districts of 
France. 



General methods for the preparation of hydroxy-acids. The 
methods available for making the hydroxy-acids are modifica- 
tions of those used for making alcohols ami acids. 

Starting with a mon-acid alcohol, wo can make a hydroxy- 
acid by the same methods which we used in making an acid 
from a hydrocarbon. Suppose, Tor example, that, we are to 
make acetic acid from marsh gas. The reactions which wo 
make use of are: (1) the preparation of a halogen derivative; 
(2) conversion of the halogen derivative into the cyanogen 



158 DERIVATIVES OF THE PARAFFINS. 

derivative ; and (3) conversion of the cyanogen derivative into 
the acid. We describe the results of these operations by saying 
that we have introduced carboxyl. By similar operations we 
can introduce carboxyl into methyl alcohol, and the product is 
hydroxy-acetic acid. 

It is, however, generally better to start with an acid, and 
introduce hydroxyl. This can be done in several ways : — 

1. By treating a halogen derivative of an acid with water or 
silver hydroxide : — 

CH2 <C0 2 H +HH ° = CH2< c5 H + HBr - 

Brom-acetic acid. 

2. By treating an amino derivative of an acid with nitrous 
acid (see page 99) : — 

CH * < cJh + HN °' = CH * < C0 2 H + N * + H *°- 

Amino-acetic acid. 

3. By treating a sulphonic-acid derivative of an acid with 
caustic potash : — 

CH2< CO H H + K ° H = CH2 "^CO H + KHS ° 3 ' 

Sulpho-acetic acid. 

The first two of these reactions have been described and men- 
tioned as affording methods for the introduction of hydroxyl 
into hydrocarbons. It will be seen that the only difference 
between the reactions used in making alcohols and those used 
in making hydroxy-acids is that in one case we start with the 
hydrocarbons, while in the other we start with the acids. 

Glycolic acid, Hydroxy-acetic acid, Oxy-acetic acid, 
Ethanolic acid, C2H403f = CH2< rn _ ). — Glycolic acid is 
found in nature in unripe grapes, and in the leaves of the wild 
grape (Ampelopsis hederacea). 



GLYCOLIC ACID, ETC. 159 

It can be made from glycocoll, which is amino-acetic acid (see 
reaction 2, above), from brom- or chlor-acetic acid and water 
(see reaction 1, above), and by the oxidation of glycol : — 

CH 2 OH C0 2 H , 

| +0 2 = | +H 2 0. 

CH 2 OP CH 2 OH 

Glycol. Q-lycolic acid. 

This consists in transforming one of the primary alcohol groups, 
CH 2 OH, contained in glycol into carboxyl. (What would be 
formed by conversion of both the primary alcohol groups of 
glycol into carboxyl ?) It can also be made by careful oxida- 
tion of ethyl alcohol with nitric acid. For this purpose a 
mixture of alcohol and nitric acid is allowed to stand until no 
further action takes place. 

Glycolic acid forms crystals that are easily soluble in water, 
alcohol, and ether. 

As an acid, glycolic acid forms a series of salts with metals, 
and ethereal salts with alcohol radicals. The latter, of which 
ethyl glycolate may be taken as an example, can be made b}- 
means of one of the reactions usually employed for making 
ethereal salts ; for example, by treating silver glycolate with 
ethyl iodide : — 

CH <<SLw + CAI = CH3< c5 CsH , + AgI - 



In this reaction, as well as in the formation of salts of glycolic 
acid, the alcoholic hydroxyl remains unchanged. 

As an alcohol, glycolic acid forms ethers of which ethyl- 

gly colic acid, CH 2 < ,, ' 2 \ may serve as an example. It will be 

seen that this is isomeric with ethyl glycolate. But while the 
Latter has alcoholic properties, the former has acid properties. 

Ethyl glycolate is a liquid which boils at 160°. Ethyl-glycolic 

acid is a liquid which boils at 206° to 207°. Finally, as an 
alcohol, glycolic acid forms ethereal salts, o( which aeetyl- 
glycolic acid may serve as an example. This is glycolic add 



160 DERIVATIVES OE THE PARAFFINS. 

in which the hydrogen of the hydroxyl is replaced by acetyl, 

CH 2 < ' 2 3 , bearing, as will be seen, the same relation to 

glycolic acid and acetic acid that ethyl acetate, C 2 H 5 .O.C 2 H 3 0, 
bears to alcohol and acetic acid. 

Glycolic acid and some of the other acids of the series lose 
water when heated, and yield peculiar anhydrides. The prod- 
act obtained from glycolic acid is called glycolide. It has 
neither acid nor alcoholic properties, and is, therefore, be- 
lieved to be derived from glycolic acid as represented in this 
equation : — 

nTT CH 2 - O - CO 

2CH2< moH =l ' +2H2 °- 

tuuil CO - O - CH 2 

Glycolide. 

Glycolide is insoluble in cold water. When boiled for a long 
time with water, it is converted into glycolic acid. 

Lactic acids, Hydroxy-propionic acids, Oxy-propionic 

acids, C 3 H 6 3 ( = C 2 H4 < ~ H J. — In speaking of propionic 

acid, it was pointed out that two series of substitution-products 
of the acid are known, which are designated as the a- and fi- 
series. Accordingly we should expect to find two hydroxy- 
propionic acids, the a- and the /3-acid. Two lactic acids 
have been known for a long time. One of these is ordinary 
lactic acid; the other a variety which is found in flesh, and 
hence called sarco-lactic acid. But, strange to say, a thorough 
investigation of these two acids has proved that both must be 
represented by the same structural formula, as both conduct 
themselves in exactly the same way towards reagents. Further, 
two other hydroxy-propionic acids are certainly known. The 
facts then are these : four acids are known, all of which are 
hydroxy-propionic acids. Our theory enables us to foretell the 
existence of only two. Before discussing this apparent dis- 
crepancy let us briefly study the acids themselves. 



LACTIC ACIDS. 161 

1. Lactic acid, inactive Ethylidene-lactic acid, a-Hy- 

droxy-propionic acid, CH 3 . CH < ®f* ^ • — Lactic acid is 

made by the fermentation of sugar, as has already been de- 
scribed under Butyric Acid (which see). The process is car- 
ried out best by dissolving cane sugar and a little tartaric acid 
in water ; then adding putrid cheese, milk, and zinc carbonate, 
the object of which is to prevent the solution from becoming 
acid, as the presence of free acid is fatal to the ferment. Lac- 
tic acid can also be made by fermentation of sugar of milk, 
and is hence contained in sour milk ; by boiling a-chlor-pro- 
pionic acid with alkalies, — 

CH 3 .CH < ^ + KOH = CH3.CH < ^ + KC1; 

and by treating alanine (a-amino-propionic acid) with nitrous 
acid, — 

OH3.CH < ^. + HN0 2 = CH 3 .CH < ^ H + N 2 + H 2 0. 

Lactic acid is a thick liquid that mixes with water and with 
alcohol in all proportions. 

When commercial lactic acid of specific gravity 1.21 is dis- 
tilled under much diminished pressure (1 mm. of mercury) and 
the distillate allowed to stand in a freezing-mixture for a time, 
it takes the form of crystals which melt at 17°. 5-18°. 

Treated with hydriodic acid, it is reduced to proprionic acid. 

CH 8 .CH < 011 +2HI = CH 3 .CH a .COj# + H 8 + I* 



2. Sarco-lactic acid, dextro-ethylidene-lactic acid. 
OFT 

CH;CH< X-^tt- — This acid occurs in the Liquids expressed 

from meat. It is therefore contained in "extract oi meat," 
and can be obtained most readily from this source. 



162 DERIVATIVES OF THE PARAFFINS. 

Its properties are, for the most part, like those of inactive 
lactic acid, and its conduct towards reagents is in all respects 
the same. Its salts are somewhat more easily soluble than 
those of ordinary inactive lactic acid. The chief difference 
between the two is observed in the action towards polarized 
light. Dextro-lactic acid turns the plane of polarization to the 
right. Its salts are all levo-rotatory. On the other hand, 
neither inactive lactic acid nor its salts exert any action upon 
polarized light. 1 

OTT 

3. Levo-lactic acid, CH 3 CH< Z,r" TT . — A third variety 

OU2±± 

of ethylidene-lactic acid, which turns the plane of polarization 
to the left, is formed from cane sugar by the action of a certain 
ferment found in a spring-water. By fractional crystallization 
of the strychnine salt of ordinary inactive lactic acid two kinds 
of crystals are obtained. The acid separated from one kind is 
sarco-lactic, or dextro-lactic, acid; while that separated from 
the other kind is levo-lactic acid. This method of splitting 
the inactive acid into the two active varieties is applicable 
to many other similar cases. The relations between these 
three acids are of the same kind as those existing between the 
three varieties of tartaric acid. 

4. Hydracrylic acid, 1 CH2OH 

r ' 

0-Hydroxy-propionic acid, J CH2CO2H 
Hydracrylic acid is made by boiling /?-iodo-propionic acid with 
water or silver oxide and water : — 

CH 2 I CH 9 .0H 

I + HHO = I + HI. 

CH 2 .C0 2 H CH 2 .C0 2 H 

CH 2 

It is made also by starting with ethylene, | . When this 

CH 2 

hydrocarbon is treated with hypochlorous acid, HOC1, it is con- 

1 See active and inactive amyl alcohols, p. 126. 



ETHYLENE-LACTIC ACID. 163 

CH 2 C1 
verted into ethylene-chlorhydrine, | (which, see). By 

CH 2 OH 

replacing the chlorine with cyanogen, and boiling the cyan- 

CH 2 OH 

hydrine, | , thus obtained, with an alkali, hydracrylic acid 

CH 2 CN 

is obtained. 

These reactions clearly show that hydracrylic acid is an 
ethylene compound, and, as it is made from /?-iodo-propionic 
acid by replacing the iodine with hydroxyl, it follows further 
that the /^-substitution-products of propionic acid are ethylene 
products, and that the a-products are ethylidene products (see 
p. 131). 

Hydracrylic acid is a syrup. Its salts differ markedly from 
those of the inactive and active lactic acids. When heated, it 
loses water and is transformed into acrylic acid, CH 2 .CH.C0 2 H 
(which see). 

The difference in conduct between ethylidene-lactic acid and 
ethylene-lactic acid, when heated, is interesting and suggestive. 
When ethylidene-lactic acid is heated, both its acid and alco- 
holic properties are destroyed, both the alcoholic and acid 
hydroxyls taking part in the reaction. Whereas, when ethyl- 
ene-lactic acid is heated, only the alcoholic properties are 
destroyed, the carboxyl remaining intact. 

There are then more hydroxy-propionic acids known than our 
theory of linkage in its simplest form can account for. Other 
cases of this kind are known, and one very marked ami 
especially interesting one will be taken up when tartaric acid 
is treated of. It will be shown that just as there are two 
active lactic acids and an inactive one, so there are two active 
tartaric acids and an inactive one, which conduct themselves in 
the same way towards reagents, and must hence be represented 
by the same structural formula. 

We have here to deal with a new kind oi' isomerism. Bodies 
may conduct themselves ehemieallv in exactly the same way, 



164 



DERIVATIVES OF THE PARAFFINS. 



and yet differ in some of their physical properties, as in their 
action towards polarized light. To distinguish this kind of 
isomerism from ordinary chemical isomerism it has been called 
physical isomerism. 

An ingenious hypothesis has been put forward by way of 
explanation of that particular kind of physical isomerism which 
shows itself in the action of compounds upon polarized light. 
It must be remembered that our ordinary formulas have nothing 
whatever to do with the relations of the atoms and groups in 
space. They indicate chemical relations which are discovered 
by a study of chemical reactions. 

Let us suppose that in a carbon compound one carbon atom 
is situated at the centre of a tetrahedron, and that the four 
atoms or groups which it holds in combination are at the angles 
of the tetrahedron, as represented in Fig. 10. 

If these groups are all different in kind, and only in this 
case, it is possible to arrange them in two ways with reference 
to the carbon atom. The difference between the two ar range- 




Fig. 10. 




ments is that which is observed between either one and its 
reflection in a mirror. Imperfectly the second arrangement 
is shown in Fig. II. 1 

A carbon atom, in combination with four different kinds of 
atoms or groups, is called an asymmetrical carbon atom. When- 
ever, therefore, a compound contains an asymmetrical carbon 



1 This can be made clear only by means of models, 
wire and wooden balls, 



These can easily be made of stout 



HYDROXY-SULPHONIC ACIDS. 165 

atom, there are two possible arrangements of its parts in space 
which correspond to the two complementary tetrahedrons, viz., 
the right-handed and the left-handed tetrahedron. 

In ethylidene lactic acid there is an asymmetrical carbon atom, 
as shown by the ordinary formula, which may be written thus : 

H 

I 
CH 3 - C - OH, the central carbon atom appearing in combination 
I 
C0 2 H 

with (1) hydrogen, (2) hydroxy 1, (3) carboxyl, and (4) methyl. 
Hence, according to the hypothesis just stated, there ought to 
be two possible arrangements of the parts of a compound con- 
taining this group, one corresponding to the right-handed tetra- 
hedron, the other to the left-handed tetrahedron. Both would 
be ethyl idene-lactic acids. The inactive variety is formed by 
the combination of the two active varieties, and must, therefore, 
have a greater molecular weight than these. 

The branch of chemistry which has to deal with the kind of 
isomerism just referred to is called stereo-chemistry. The 
phenomena of stereo-chemistry have been the subject of exten- 
sive investigation, and the facts established furnish a strong 
foundation for the theory briefly expounded above. 

Hydroxy-sulphonic acids It has been pointed out that 

the sulphonic acids and the carbonic acids are analogous : that, 
for example, methyl-sulphonic acid, OH.. .S0 3 H, is analogous to 
methyl-carbonic or acetic acid, CH 3 .CO a H. Now, just as the 
hydroxy -acids already treated of arc derived from the carbonic 
acids by the introduction of hydroxyl, so there arc hydroxy 
acids derived iu a, similar way from the sulphonic acids. 
Only one such acid is well known. It is — 

Isethionic acid, C-jHi^.^" also called fi-hydroxy-ethyl- 

sulphonic acid. In composition it is analogous to the hydroxy- 
propionic acids. It is prepared by passing sulphur trioxide into 



166 DERIVATIVES OF THE PARAFFINS. 

well cooled alcohol or ether and boiling the product with water; 
and also by treating taurine (which see) with nitrous acid: 

CH 2 .NH 2 CH 2 OH 

| + HNO, = | + H 2 + N 2 . 

CH 2 .S0 3 H CH 2 .S0 3 H 

Lactones. 

The monohydroxy-monobasic acids of the paraffin series are 
designated as a-, /?-, y-, S-, etc., acids, according to the position 
of the hydroxy 1 with reference to the carboxyl. When the 
hydroxyl is united with the carbon atom with which the car- 
boxyl is united the product is called an cc-hydroxy-acid. When 
the hydroxyl is united with the next carbon atom in the chain 
the product is called a /3-hydroxy-acid, etc. The following 
examples will make this clear : — 

Acids of the formulas 

CH 2 (OH).C0 2 H, CH 3 .CH(OH).C0 2 H, CH 3 .CH 2 .CH(OH).C0 2 H 

are a-hydroxy-acids. 
Acids of the formula 

CH 2 (OH).CH 2 .C0 2 H, CH 3 .CH(OH).CH 2 .C0 2 H, 
CH 3 .CH 2 .CH(OH).CH 2 .C0 2 H are /?-hydroxy-acids. 

Acids of the formulas 

CH 2 (OH).CH 2 .CH 2 .C0 2 H, etc., are y-hydroxy-acids. 

Similarly an acid of the formula 

CH(OH).CH 2 .CH 2 .CH 2 .C0 2 H is called a S-hydroxy-acid. 

The y- and S-acids differ from the others in this respect that 
they lose the elements of water when set free from their salts. 
Thus, when a salt of y-hydroxy-butyric acid in solution is 
treated with a mineral acid, a neutral compound is precipitated 
and not the acid corresponding to the salt. The compound 
thus formed is called a lactone. The reaction between sodium 



HYDROXY-ACIDS, C n H 2n 4 . 167 

y-hydroxy-butyrate and hydrochloric acid is represented by the 
following equation : — 

CH 2 (OH) .CH 2 .CH 2 .C0 2 Na + HC1 
= CH 2 .CH 2 .CH 2 .CO + NaCl + H 2 0. 

L— o 1 



The change from the free acid to the lactone may be repre- 
sented thus : — 

CH 2 .CH 2 (OH) CH, .CH 2 . 
I =1 >0 + H 2 0. 

CH 2 .CO OH CH 2 .CO ' 

The reaction is similar to that which takes place when suc- 
cinic acid is heated : — 

CH 2 .CO.OH CHo.COv. 
| =| >0 + H 2 0. 

CH 2 .CO.OH CH 2 .C(K 

The product in this case is an anhydride. The lactones may 
be denned as anhydrides of hydroxy-acids. They are neutral, 
but they form the salts of the corresponding hydroxy-acids 
when they are boiled for some time with bases in solution. 

Hydroxy-acids, C n H, n 4 . 

The acids just treated of are called rnonohydroxy-monobasxc 
acids. Similarly, there are dihydroxy-monobasic acids, which 
are derived from the monohydroxy-acids by the introduction of 

a second hydroxyl. Thus, if into lactic aoid, CHs.CH< ^ > 

a hydroxyl should be introduced into the methyl, the product 

CHa.OH 

I 
would have the formula CH.OH. This is fche best known 

I 
CO a H 

dihydroxy-monobasic acid of the paraffin series. 



168 DERIVATIVES OF THE PARAFFINS. 



Glyceric acid, Propandiolic acid, C3H6O4 



CH2OH 
= CHOH 
CO2H 



This acid has been referred to as the first product of the oxida- 
tion of glycerol. It is prepared by allowing glycerol and nitric 
acid to stand together at the ordinary temperature for some 
time, and then heating on the water-bath. It can also be made 
by treating /?-chlor-lactic acid with water. 

An optically active variety of glyceric acid has been obtained 
from the inactive variety. It will be seen that the acid con- 
tains an asymmetric carbon atom. 

Glyceric acid is a thick syrup which mixes with water and 
alcohol. When treated with very concentrated hydriodic acid, 
it is converted into /?-iodo-propionic acid. This conversion 
involves two reactions : — 

CH 2 OH CH 2 I 

I I 

(1) CHOH + HI = CHOH + H 9 0, and 

I I 

C0 2 H C0 2 H 

CH 2 I CH 2 I 

I I 

(2) CHOH + 2 HI = CH 2 + H 2 + 2 1. 

I I 

C0 9 H C0 9 H 



Other Hydroxy-monobasic Acids. 

Just as by oxidation of the tri-acid alcohol glycerol, a dihy- 
droxy-monobasic acid can be formed, so by oxidation of the 
tetr-acid alcohol, erythrol, a trihydroxy-monobasic acid can be 
formed. This is erythritic acid. Its relation to erythrol is like 
that of glyceric acid to glycerol : — 



OTHER HYDROXY-MONOBASIC ACIDS. 



169 



CH 2 OH 

I 

CHOH 

I 
CH 2 OH 

Glycerol. 



CH 2 OH 

I 
CHOH 

I 
C0 2 H 

Glyceric acid. 



CH 2 OH 

I 
CHOH 

I 
CHOH 

I 
CH 2 OH 

Erythrol. 



CH 2 OH 

I 
CHOH 

I 
CHOH 

I 
C0 2 H 

Erythitic acid. 



Similarly from the pent-acid alcohols tetrahydroxy-mono- 
basic acids, and from the hex-acid alcohols, pentahydroxy- 
monobasic acids can be made. The latter are of special 
importance on account of their connection with the sugars. 



Mannonic acids, C 6 Hi 2 07(= CsHe (OH) 5CO2H). — Three 

acids are included in this group. They are the dextro, the levo, 
and the inactive varieties, or d- 1 mannonic, I- 1 mannonic, i- 1 man- 
nonic acids. They are related to the three mannites and the 
three mannoses. As will be shown further on the mannoses 
are pentahydroxy-aldehydes and the relations here referred to 
are represented by the following formulas : — 

CH 2 OH CH 2 OH CH 2 OH 



CHOH 

I 
CHOH 

I 
CHOH 

I 
CHOH 

I 
CH.,011 



CHOH 

I 
CHOH 

I 
CHOH 

I 
CHOH 

I 
COH 



CHOH 

I 
CHOH 

I 
CHOH 



CHOH 

I 
CO,H 

Mannonio acid. 



The difference between the three mannonic acids is o( the same 
kind as that between the Hirer lact lc acids. The dextro and levo 
varieties are complementary forms, while the inactive variety is 
formed by a combination of the dextro and levo varieties. 



1 Instead of using the prefixes d&otro' and fovo-, 
to use the letters d . ! . and i 'is the} are here used 



and tlio word inactiVt 



170 DERIVATIVES OF THE PARAFFINS. 

Gluconic acids, CeH^OT^CsHeCOH^CCXE). — The glu- 
conic acids are related to the three glucoses in the same way 
that the mannonic acids are related to the mannoses. Dextro- 
glaconic acid is formed by the oxidation of glucose and of cane 
sugar. When heated with quinoline to 140°, it is partly con- 
verted into d-mannonic acid. Similarly d-mannonic acid is 
partly converted into cZ-gluconic acid by the same process. 
Three Gulonic acids and three Galactonic acids of the 
same composition and structure as the mannonic and the glu- 
conic acids are also known. 

The existence of so many acids of the formula C 5 H 6 (OH) 5 C0 2 H 

is due to the fact that a substance made up as represented in 

the formula 

CH 2 OH 

I 
CHOH 

I 
CHOH 

I 
CHOH 

I 
CHOH 

I 
C0 2 H 

contains four asymmetric carbon atoms, each one of which 
carries with it the possibility of the existence of three varieties. 
This subject will be more fully discussed under the sugars. 

Hydroxy-acids, C n H 2n _ 2 5 . 

The acids included under this head are monohydroxy-dibasic 
acids. They bear the same relation to the dibasic acids of the 
oxalic acid series that the simplest hydroxy-acids bear to the 
members of the formic acid series. The principal members of 
this series, and the only ones which will be treated of, are 
tartronic acid and malic acid. 



MALIC ACID. 171 

Tartronic acid, C 3 H 4 5 (=CH(OH)<^^). — This acid 
is prepared by an indirect method from tartaric acid. It can 
be made, — 

(1) By boiling brom-malonic acid with silver oxide and 
water : — 

CHBr<gjg + AgOH = CH(OH)<gjg + AgBr; 

(2) By treating brom-cyan-acetic acid with caustic potash : — 

CHBr < ^ + 2 KOH + H 2 
CU2-H- 

= CH(OH) <^K + NHs + KBr 

Tartronic acid is a solid which crystallizes in prismatic crys- 
tals. It is easily soluble in water, alcohol, and ether. The 
anhydrous acid melts at 185-187° with evolution of carbon 
dioxide and water, and forms glycolide (which see) : — 

(!) CH(OH)<JgH =CH2< 0H ii + C02 _ 

Glycolic acid. 

n „ CH., - O - CO 

(2) 2CH 2 < Uil =| I +2H.,0. 

COOH CQ _ Q CHa 

Glycolide. 

Note for Student. — Compare reaction (1) with that which takes 
place when iso-succinic acid is heated, and note the analogy. 

Hydroxy-succinic acids, 4 H 6 O 6 ( C,H ;! (OHX CO - H Y — 

\ CO H 

Lhree hydroxy-succinic acids have been described, the principal 

one being ordinary malic acid. 

/ CH(OH).CO.H\ 
Malic acid, C,H,A = I . — This acid is very 

V CH,..CO,H / 
widely distributed in the vegetable kingdom, as in the berries 

of the mountain ash, in apples, cherries, etc. 

It is best prepared from the berries of the mountain as!: 



172 DERIVATIVES OE THE PARAFFIN'S. 

which have not quite reached ripeness. The berries are pressed 
and boiled with milk of lime. The acid passes into solution as 
the calcium salt, and this is purified by crystallization. 

It can also be made by treating aspartic acid, which is amino- 

PO H 
succinic acid, C 2 H 3 (NH 2 ) < „„ 2 „, with nitrous acid, and by treat- 
C(_) 2 H 

ing tartaric acid with hydriodic acid. This latter reaction will 

be explained when tartaric acid is considered . Tartaric and 

malic acids are closely related to each other, and both are 

related to succinic acid, as will appear from the reactions. 

Malic acid is a solid substance which crystallizes with diffi- 
cult}'. It is very easily soluble in water and in alcohol. Its 
solutions turn the plane of polarization to the right or to the left, 
according to the concentration. 

When heated it loses water and yields either fumaric or 
maleic acid (which see), according to the temperature. These 
acids are isomeric, and both are represented by the formula 

C 2 H 2 < ro 2 n - The reaction mentioned is represented by the 

following equation : — 

C 2 H 3 (OH)<COg = C 2 H 2 <CO| + H2 o. 

>» ,. . , Fumaric or 

Mahc acid ' maleic acid. 

Note for Student. — Compare this reaction with that which takes 
place when hydracrylie acid is heated, and note the analogy. 

When treated with hydriodic acid, malic acid is reduced to 
succinic acid. 

Note for Student. — Compare this reaction with the conduct of 
lactic and glyceric acids when treated with hydriodic acid. 

Treated with hydrobromic acid, malic acid is converted into 
mono-brom-succinic acid. 

The reactions just described show clearly that malic acid is 
hydroxy-succinic acid. Nevertheless, if hydroxy-succinic acid 
is made by treating brom-succinic acid with silver oxide and 



INACTIVE MALIC ACID. 173 

water, the product is not identical with ordinary malic acid, 
though the two resemble each other very closely. The acid 
thus obtained is — 

Inactive malic acid, C 2 H 3 ( OH )< qq 2 ^- — Inactive malic 

acid can be made not only by the method first mentioned, but 
by several others, which indicate that the relation between it 
and succinic acid is that expressed in the formula given. It, 
like ordinary malic acid, is unquestionably a hydroxy-succinic 
acid, and both are derived from ordinary succinic acid. 

Other reactions for the preparation of inactive malic acid 
are,— 

(1) By treating dichlor-propionic acid with potassium cyanide, 
and boiling the product with caustic potash : — 

CH 2 C1.CHC1.C0 2 H + KCN 
CEUCN 
= I +KC1; 

CHCl.COoH 

CH 2 CN 
and | +2 KOII + H 2 

CHC1.C0 2 H 

CHo.CO,K 
= | + KC1 + NH S . 

CH(OII).COoII 

(2) By heating fumaric acid with water : — 

c ^<coS + H! ° = CaH8(OH)< SS !Mld 

(8) By reduction of racemic acid with hydriodic acid. Ra- 
cemic acid has the same composition as tartaric acid. The 
latter, when treated with hydriodic acid, yields active malic 
acid. 

The properties of inactive malic acid are very much like 
(hose of active malic acid. As regards their chemical conduct 



174 DERIVATIVES OF THE PARAFFINS. 

they are almost identical. The principal difference between 
them is observed in their conduct towards polarized light. 
They present a new case of physical isomerism of the same 
kind as that referred to in connection with the lactic acids 
(which see) . 

Dextro-malic acid. — Inactive malic acid bears the same 
relation to two active acids that inactive lactic acid bears to the 
two active varieties of that acid. When the cinchonine salt of 
inactive malic acid is subjected to fractional crystallization, two 
different salts are obtained. One of these is derived from 
ordinary levo-malic acid, while the other is derived from the 
isomeric dextro-malic acid. 

Hydroxy- acids, C n H 2n _ 2 6 . 

These are di-hydroxy -dibasic acids. The chief members of 
the group are mesoxalic acid and the different modifications 
of tartaric acid. 

Mesoxalic acid, C 3 H 4 6 (= C(OH) 2 < qq^Y — ™ s acid 

is obtained by indirect and rather complicated reactions from 
uric acid (which see) . It has been made also by boiling di- 
brom-malonic acid with baryta-water. 

Note for Student. — Explain this reaction. 

The acid forms deliquescent needles. "When boiled it loses 
carbon dioxide and water, and glyoxylic acid, which is an alde- 
hyde and acid related to oxalic acid, is formed : — 

C(OH) 2 <^£ = | + C0 2 + H 2 0. 
OU2il C0 2 H 

Glyoxylic acid. 

This acid affords an example of a very rare condition; viz., 
the existence of a compound in which two hydroxyls are in 
combination with one and the same carbon atom. 



TARTARIC ACID. 175 

Di-hydroxy-succinic acids, C 4 H 6 6 ( = C 2 H 2 (OH) 2 < co Vj. J. 

CH(OH).0O 2 H 
1. Tartaric acid, I . — Ordinary tartaric acid 

CH(OH).0O 2 H 
occurs very widely distributed in fruits, sometimes free, some- 
times in the form of the potassium or calcium salt ; as, foi 
example, in grapes, berries of the mountain ash, potatoes, 
cucumbers, etc., etc. 

It can be made by the following methods : •— 

(1) By oxidizing sugar of milk with nitric acid ; 

(2) Also by oxidizing cane sugar, starch, glucose, and other 
similar substances. 

Tartaric acid is prepared from "tartar," which is impure 
acid potassium tartrate. When grape juice ferments this salt 
is deposited. It is purified by crystallization, converted into 
the calcium salt by treating it with chalk, and the calcium salt 
then decomposed b}^ means of sulphuric acid. 

The acid crystallizes in large monoclinic prisms, which are 
easily soluble in water and alcohol. It melts at 168-170°. Its 
solution turns the plane of polarization to the rigid. 

Treated with hydriodic acid, tartaric acid yields first malic 
acid and then ordinary succinic acid : — 

(1) C 2 H 3 (OH) 2 <jgH + 2H I 

= C,II 3 (OTI)<^J|+ILO + I 3 ; 

Malic add. 

(2) C 2 H 3 (OII)<^JJ+2III 

Buooinlo add. 

While malic acid is mono-hydroxy-succinic acid, ordinary 

tartaric; acid appears to he di-hydroxv -succinic acid. But, just 



176 DERIVATIVES OF THE PARAFFINS. 

as the malic acid prepared from mono-brom-succinic acid is 
optically inactive, and therefore different from natural, active 
malic acid, so too the tartaric acid prepared from di-brom-suc- 
cinic acid is optically inactive, and therefore different from 
ordinary tartaric acid. The relations between the natural and 
the artificial acids will be considered more fully below. 

Tartrates. Among the salts the following may be mentioned : 

Mono-potassium tartrate, KH . C 4 H 4 6 . This is the chief 
constituent of tartar. In pure form, as used in medicine, it is 
known as cream of tartar. 

Sodium-potassium tartrate, KiSTa . C 4 H 4 6 + 4 H 2 0. This 
salt crystallizes very beautifully. It is known as Rochelle salt 
or Seignette salt. Seidlitz powders consist of (1) a mixture of 
Rochelle salt and sodium bicarbonate, and (2) tartaric acid. 
These are dissolved separately and then brought together, when 
a rapid evolution of carbon dioxide takes place. 

Calcium tartrate, Ca.C 4 H 4 6 + 4 H 2 0. This salt occurs in 
senna leaves and in grapes. It forms a crystalline powder or 
rhombic octahedrons. 

Potassium - antimonyl tartrate, K ( SbO ) . C 4 H 4 6 + ^ H 2 . 
This is known as tartar emetic. It is prepared by digesting 
antimonic oxide with mono-potassium tartrate. It crystallizes 
in rhombic octahedrons. It loses its water of crystallization at 
100°, and at 200 to 220° is converted into an antimony potas- 
sium salt of the formula KSb .C 4 H 2 6 . 

2. Racemic acid, C 4 H 6 6 + H 2 0. — Racemic acid occurs, 
together with tartaric acid, in many kinds of grapes, and, on 
recrystallizing the crude tartar, acid potassium racemate, being 
more soluble than the tartrate, remains in the mother liquors. 
Racemic acid is formed by boiling ordinary tartaric acid with 
water, or with hydrochloric acid. If tartaric acid is heated 
with water in sealed tubes at 175°, it is almost completely 
transformed into racemic acid. It is formed further by oxida- 
tion of dulcite, mannite, cane sugar, gum, etc., with nitric 
acid. It, together with a third variety of tartaric acid, known as 



RACEMIC ACID. 177 

inactive tartaric acid, is formed when dibrom- succinic acid is 
treated with silver oxide and water. 

Kacemic acid differs from tartaric acid in many ways. It 
crystallizes differently, and contains water of crystallization. 
It is less soluble than tartaric acid. It produces precipitates 
in solutions of lime salts, while tartaric acid does not. Racemic 
acid is optically inactive, while tartaric acid is dextro-rotatory. 
On the other hand, racemic and tartaric acids conduct them- 
selves towards most reagents exactly alike. 

The relations between racemic and tartaric acid are the same 
as those which have already been referred to as existing between 
inactive malic acid and dextro-malic acid, and between inactive 
lactic and dextro-lactic acid. This case is, however, of special 
interest, as it was the first one of the kind studied. The relations 
were discovered by means of the experiment described below. 

When a solution of ammonium-sodium racemate, 

(NH 4 )Na.C 4 H 4 6 , 

is allowed to evaporate spontaneously, beautiful large crystals 
are deposited. On examining these carefully, they are found 
to be of two kinds. On the crystals of one kind certain hemi* 
hedral faces are developed, while on the crystals of the other 
kind the complementary hemihedral faces are developed ; so 
that if a crystal of one kind is placed in front of a mirror, 
its reflection will represent the arrangement of the hemihedral 
faces met with on a crystal of the other kind. The crystals 
can be separated into right-handed^ or those which have the 
right-handed hemihedral faces, and left-handed, or those which 
have the left-handed hemihedral faces. 

On separating the acid from the right-handed crystals it is 
found to be ordinary dextro-rotatory tartaric acid; while the 
acid from the left-handed crystals is an isomeric substance 
called hvro-rofatorj/ tartaric acid. When these two varieties 
of tartaric acid are brought together in solution, they unite, the 
action being attended by an elevation of temperature, and tin- 
result is racemic acid. 



178 DERIVATIVES OF THE PARAFFINS. 

By crystallizing cinchoniiie racemate from alcohol it can be 
resolved into dextro and levo varieties, from which the corre- 
sponding active acids can be obtained. 

We see thns that the inactive racemic acid consists of two 
optically active substances in combination, one of which, ordi- 
nary tartaric acid, is dextro-rotatory, and the other levo-rotatory. 

As has already been stated, both inactive malic acid and in- 
active lactic acid have been resolved into two active varieties, 
one of which is dextro-rotatory, and the other levo-rotatory. 

3. Inactive tartaric acid, Mesotartaric acid, C4H4O6 

+ H2O, is very similar to racemic acid. It is formed together 

with racemic acid by treating di-brom-succinic acid with silver 

oxide and water. 

The tartaric acids contain two asymmetric carbon atoms, 

OH 

I 
H - C - C0 2 H 

I . If the groups and atoms be arranged in the 

H - C - C0 2 H 
I 
OH 

same way about both of them, the compound will be optically 
active, either dextro or levo rotatory. If arranged in the op- 
posite way about both asymmetric carbon atoms, the comple- 
mentary stereoisomeric form will result. A combination of the 
two active forms will give the inactive form. 

On the other hand, the groups may be arranged in one way 
about one asymmetric carbon atom and in the other possible 
way about the other asymmetric carbon atom. The resulting 
compound will be inactive by internal compensation, and will 
not be capable of resolution into two active varieties. This 
latter arrangement is that of mesotartaric acid. 

Hydroxy-acids, C n H 2n _ 4 7 . 

These are mono-hydroxy-tribasic acids. Citric acid is the 
only one known. 



CITRIC ACID. 179 

/ rC0 2 H\ 

Citric acid, CeHsO + H2O = C 3 H 4 (OH) \ CO2H ). — Citric 

n ICO2H' 

acid, like malic and tartaric acids, is very widely distributed in 
nature in many varieties of fruit, especially in lemons, in which 
it occurs in the free condition. It is found in currants, whortle- 
berries, raspberries, gooseberries, etc., etc. 

It is prepared from lemon juice, and also by the fermentation 
of glucose by citromycetes pfefferianus and a few other ferments. 
After the fermentation the mass is treated with lime. The 
lime salt thus obtained in the form of a precipitate, is collected, 
and decomposed with sulphuric acid. One hundred parts of 
lemons yield 5J parts of the acid. 

Citric acid crystallizes in rhombic prisms which are very 
easily soluble in water. The crystallized acid melts at 100°, 
the anhydrous at 153° to 154°. Heated to 175° it loses water 
and yields aconitic acid (which see) : — 

( C0 2 H ( C0 2 H 

C 3 H 4 (OH) } C0 2 H = C3H3 ) C0 2 H + H 2 0. 
( C0 2 H ( C0 2 H 

Aconitic acid. 

Note for Student. — Compare with formation of acrylic from 
hydracrylic acid ; and of male'ic and fumaric acids from malic acid. 

Aconitic acid takes up hydrogen, and is transformed into 
tricarballylic acid (which see). Thus a clear connection be- 
tween tricarballylic acid and citric acid is traced; the latter 
is hydroxy-tricarballylic acid. Citric acid may be made from 
CIL.CO.,11 
I 
acetone-dicarbonic acid, CO by I real ingthis with hvdro- 

I 
CH,.(H),1I 

cyanic acid and saponifying 1 t he nitril thus formed: 

1 The conversion of a nitril into the corresponding oarboxyl oompound is generally 
called saponification, though, strictly speaking, it la not the same reaction aa saponl 

proper. 



180 DERIVATIVES OF THE PARAFFINS. 

CH 2 .C0 2 H CH 2 .C0 2 H 

I I HIT 

CO +HCN = C< 



CN 
CH 2 .C0 2 H CH 2 .C0 2 H 

CH 2 .C0 2 H CH 2 .C0 2 H 

OTT OH 

°<w + 2H *° = ( ;<co 2 h +NH =- 

CH 2 .C0 2 H CH 2 .C0 2 H 

This synthesis shows that the hydroxyl in citric acid is in 
combination with the central carbon atom. 

When rapidly heated to a temperature above 175°, citric acid 
first gives aconitic acid, then loses water and forms the cor- 
responding anhydride, which in turn loses carbon dioxide and 
gives itaconic anhydride (see itaconic acid). This latter anhy- 
dride is then partly converted into citraconic anhydride (see 
citraconic acid) by the action of heat. 

Citrates. A few of the salts of citric acid are : — 

Mono-potassium citrate, KH 2 . C 6 H 5 7 + 2 H 2 ; 

Di-potassium citrate, K 2 H . C 6 H 5 7 ; 

Tri-potassium citrate, K 3 . C 6 H 5 7 + H 2 0. All these potas- 
sium salts are easily soluble in water. They are made by 
mixing citric acid and potassium carbonate in the right pro- 
portions. 

Calcium citrate, Ca 3 (C 6 H 5 7 ) 2 -f 4 H 2 0. This salt is formed 
by mixing a citrate of an alkali with calcium chloride. It is 
more easily soluble in cold than in hot water ; hence boiling 
causes a precipitate in dilute solutions. 

Magnesium citrate, Mg 3 (C 6 H 5 7 ) 2 + 14 H 2 0. This is made by 
dissolving magnesia in citric acid. It is used in medicine. 

Hydeoxy-acids, C n H 2n _ 2 8 . 

It has been pointed out that the hex-acid alcohols are con- 
verted by oxidation into pentahydroxy-monobasic acids, By 



SACCHARIC ACID. 181 

further oxidation these pentahydroxy-monobasic acids are 
converted into tetrahydroxy-dibasic acids. Thus glucose, 
CH 2 OH(CHOH) 4 CH 2 OH, when oxidized, yields, first, glu- 
conic acid, CH 2 OH(CHOH) 4 C0 2 H, and then saccharic acid, 
C0 2 H(CHOH) 4 C0 2 H, a tetrahydroxy-dibasic acid. Correspond- 
ing to each gluconic acid there is a saccharic acid. So also the 
mannonic acids yield manno saccharic acids, which are dibasic 
and isomeric with the saccharic acids; and galactonic acid 
yields mucic acid. The best known members of this group are 
saccharic and mucic acids. 

Saccharic acid, CeHioOsf^ C4H 4 (OH)4<2q"S)— The 

dextro variety is formed by the oxidation of cane sugar, 
d-glucose, sugar of milk, or starch with nitric acid. 

It is an amorphous mass that becomes solid only with 
difficulty. When treated with hydriodic acid it is reduced to 
adipic acid, a member of the oxalic acid series (see table, page 
142) : — 

C 4 H 4 (OH) 4 < gjg + 8 HI = C 4 H 8 < ^jj + 4 H 2 + 8 I. 

Saccharic acid. • Adipic acid. 

Mucic acid, C6Hio08(=04H4(OH)4<^^y_ This is 

formed by the oxidation of sugar of milk, the gums, dulcite, 
or galactose with nitric acid. It is best prepared from sugar 
of milk. 

It is a crystalline powder which is very difficultly soluble 
in cold water. Hydriodic acid reduces it to adipic acid (see 
above, under Saccharic acid). 

When heated with pyridine to 140°, mucic acid is changed 
to the isomeric form, allomiieic acid. 



CHAPTER XI. 
CARBOHYDRATES. 

Among the mixed compounds are the important substances 
commonly known as carbohydrates. This name was originally 
given to them because they consist of carbon in combination 
with hydrogen and oxygen, which two elements are present 
in the proportion to form water, as shown in the formulas, for 
glucose, C 6 H 12 6 , starch, C 6 H ]0 O 3 , etc. In view of recent dis- 
coveries the name is no longer accurate, as some substances 
belonging to this group are now known that do not contain 
hydrogen and oxygen in the proportion to form water. Such 
a substance, for example, is rhamnose, C 6 H 12 5 . The name 
carbohydrate has, however, been used so long that it would be 
difficult to supplant it. 

The carbohydrates may be conveniently classified under three 
heads. These are : — 

1. Monosaccharides or simple sugars. — Examples of these 
are glucose, fructose, arabinose, and mannose. 

2. Polysaccharides or complex sugars. — Examples are cane 
sugar, sugar of milk, maltose, and isomaltose. 

3. Polysaccharides, not resembling sugars. — Examples are 
cellulose, starch, and gums. 

The monosaccharides are the simplest carbohydrates. Those 
that are best known have the composition, C 6 H 12 6 , and are 
related to the hex-acid alcohols, sorbite and mannite, C 6 H 8 (OH) 6 . 
There are, however, simpler ones, such as arabinose, C 5 H 10 O 5 , 
erythrose, C 4 H 8 4 , and glycerose, C 3 H 6 3 ; and some that are 
more complex, as heptose, C 7 H 14 7 , octose, C 8 H 16 8 , and nonose, 
C 9 H 18 9 . The monosaccharides, therefore, fall into classes 
which are called trioses, tetroses, pentoses, hexoses, etc., accord- 
ing to the number of oxygen atoms contained in them. 



GLYCEROSE. 183 

By methods which will be explained below, it has been shown 
that the monosaccharides or simple sugars are aldehyde-alcohols 
(aldoses) or ketone-alcohols (ketoses). 

1. Monosaccharides. 

A. Trioses and Tetroses. 

Glycerose, 3 H 6 O 3 . — This sugar deserves special mention 
as being the simplest member of the group of monosaccharides, 
and as having been obtained artificially. It is formed by treat- 
ing glycerol with mild oxidizing agents, as, for example, bromine 
and sodium hydroxide. It is a mixture of glyceric aldehyde 
and dioxyacetone, the relations of which to glycerol are shown 
by the following formulas : — 

CH 2 OH CHO CH 2 OH 

I I I 

CHOH CHOH CO 

I I I 

CH 2 OH CH 2 OH CH 2 OH 

Glycerol. Glyceric aldehyde. Dioxy-acetone. 

Glycerose is a syrup that undergoes fermentation and reduces 
alkaline solutions of copper salts, acting thus like many of the 
sugars, as will be shown. Glyceric aldehyde is a simple ex- 
ample of an aldose or aldehyde-alcohol, and dioxy-acetone is 
the simplest example of a ketose or ketone-alcohol. 

When the mixture of these two substances is treated with 
caustic soda it is converted into i-acrose, a sugar of special 
importance, as it forms the starting point in the synthetical 
operations that lead to the formation of all the members o\' the 
glucose group. 

Erythose, C.,H s O.,, has been obtained from ervthrite in the 
same way that glycerose is obtained from glycerol. 

B. Pentoses. 

Arabinoses, C-HkA,. — Ordinary arabinose is obtained 
from cherry gum by boiling with dilute sulphuric acid. This 



184 CARBOHYDRATES. 

variety is called levo-arabinose on account of its relation to 
levo-glucose and levo-mannose, although it turns the plane of 
polarization to the right. Dextro-arabinose and inactive arabi- 
nose have also been obtained, the latter by combination of the 
levo and dextro varieties. 

Xylose, C 5 H 10 O 5 , is obtained from wood gum by boiling 
with dilute acids. 

Rhamnose, C 6 H 12 5 , has been obtained by the breaking 
down of a number of natural substances, such as quercitrin. It 
has been shown to be a methyl derivative of a pentose, and is 
therefore to be represented by the formula CH 3 .C 5 H 9 5 . 

C. Hexoses. 

Glucose, grape sugar (dextrose), C 6 H 12 6 . — Glucose 
occurs very widely distributed in the vegetable kingdom, 
especially in sweet fruits, in which it is found together with an 
equivalent quantity of fructose or fruit sugar. It is also found 
in honey, together with fructose ; and, further, in the blood, in 
the. liver, and in the urine ; and in the disease Diabetes mellitus, 
the quantity contained in the urine is largely increased, reaching 
as high as 8 to 10 per cent. 

Glucose is formed from several of the carbohydrates of the 
formulas C^H^On and C 6 H 10 O 5 , by boiling with dilute mineral 
acids, or by the action of enzymes. 1 The formation from cane 
sugar takes place according to this equation, equivalent quanti- 
ties of glucose and fructose being formed : — 

C 12 H220 n + H 2 = C 6 H 12 6 + C 6 H 12 6 . 

Cane sugar. Glucose. Fructose. 

Starch, cellulose, and dextrin yield glucose according to this 
equation : — 

C 6 H 10 O 5 + H 2 = C 6 H 12 6 . 

1 Enzymes, substances of the order of albumin, have the power to bring about important 
changes in some of the carbohydrates. They are called unorganized ferments, as they act 
in general like the organized ferments or ferments proper. Among the important enzymes 
are diastase and invertin. 



CARBOHYDRATES. 185 

Finally, glucose occurs in nature, in combination with a 
number of carbon compounds, in the so-called glucosides. These 
break up easily when treated with dilute mineral acids or fer- 
ments, and yield glucose as one of the products (see Glucosides). 
Examples of the glucosides are amygdalin, sesculin, salicin, etc. 

Glucose is prepared on the large scale from corn starch in 
the United States, and from potato starch in Germany. The 
transformation is usually effected by boiling with dilute sul- 
phuric acid. The excess of acid is removed by treating the 
solutions with chalk, and filtering. The filtered solutions are 
evaporated down either to a syrupy consistency, and sent into 
the market under the names "glucose," " mixing syrup," etc., 
or to dryness, the solid product being known in commerce as 
"grape sugar." By evaporating the solutions down to such 
a concentration that they contain from 12 to 15 per cent of 
glucose, crystals are formed which closely resemble those of 
cane sugar. They consist of anhydrous grape sugar. Their 
formation is facilitated by adding a little of the crystallized 
substance to the concentrated solutions. 

If in the treatment of starch with sulphuric acid the trans- 
formation is not complete, and this is usually the case, the 
product is a mixture of glucose, maltose, aud dextrin. The 
longer the action continues, the larger the percentage of glucose. 

Glucose crystallizes from concentrated solutions, usually in 
crystalline masses consisting of minute six-sided plates. The 
mass, as seen in commercial "granulated grape sugar," looks 
very much like granulated sugar. It crystallizes from alcohol 
in monoclinic crystals. The sweetness of glucose is to that of 
cane sugar as 3 to 5. Its solutions turn (he plane of polariza- 
tion to the right. 

Glucose is easily oxidized, reducing the salts of silver and 
copper. When treated with nascent hydrogen, it yields Sorbite 
(which see). Under the influence o\' yeast it ferments, yielding 
mainly alcohol and carbon dioxide. Putrid cheese transforms 
it first into lactic acid and then into butyric acid by the so-called 
lactic acid fermentation. 



186 GLUCOSE. 

Glucose forms compounds with metals and salts. Among 
the better known compounds of this kind are those mentioned 
below : — 

Sodium glucose .... C 6 H n 6 . Na ; 

Sodium chloride glucose . 2 C 6 H 12 6 . NaCl + H 2 ; 

also CeHiA . NaCl + \ H 2 0, and C^Og . 2 NaCl. These com- 
pounds, with sodium chloride, crystallize well, and can be easily 
obtained in pure condition. 

Cupric oxide glucose . . . CgH^CVo CuO. 

By treatment with acetic anhydride, glucose yields a product 
containing five acetyl groups, pent-acet}'l-glucose, 

C 6 H 7 (C 2 H 3 0) 5 6 . 

Note for Student. — What does the formation of this compound 
indicate ? 

It is often important to know the quantity of glucose con- 
tained in a given liquid ; as, for example, in the urine in a case 
of suspected diabetes. For the purpose of making the estima- 
tion, advantage is taken of the action of glucose towards an 
alkaline solution of copper sulphate. The solution commonly 
used is that known as Feliling's solution. It is prepared by 
dissolving 34.64 g crystallized pure copper sulphate in 200 cc 
water, adding a solution of 150^ potassium tartrate, and 90" 
sodium hydroxide, and diluting so that the whole makes one 
litre. 

Experiment 38. Make half the quantity of Fehling's solution 
above mentioned, and put in a bottle with a glass stopper. In a test- 
tube boil about 10 cc of this solution, and then add a few drops of a 
dilute solution of glucose. Continue to boil, and add a little more of 
the glucose solution ; and so on, until, on removing the tube from the 
lamp, a dark-red uniform-looking precipitate settles, leaving the liquid 
above it perfectly clear and colorless. This precipitate is cuprous 
oxide. By taking proper precautions, the exact amount of glucose 
present in a solution can be estimated in this way. 



CARBOHYDRATES. 187 

Ordinary glucose is known as cZ-glucose on account of its 
dextro-rotatory power. Both Z-glucose and i-glucose have been 
made. 

Fructose, fruit sugar (levulose), C 6 Hi 2 6 . — This sugar 
occurs together with glucose, and in equivalent quantities, in 
fruits ; and is formed by the action of dilute mineral acids, or 
ferments, on cane sugar. Pure fructose is obtained by heating 
inulin, a carbohydrate of the formula C 12 H 2 o0 10 , with very dilute 
acids. It is also formed by the oxidation of d-mannite. 

Ordinary fructose is called d-fructose, although it turns the 
plane of polarization to the left. The reason for this is that it 
is related to other substances that are dextro-rotatory. 

Fructose can be obtained in the form of crystals. It is about 
as sweet as cane sugar, and has been proposed as a substitute 
for this in diabetes. 

^-Fructose has been made artificially in three ways : — 

1. By polymerisation of formic aldehyde, CH 2 0, by means 
of bases ; 

2. By successive treatment of acrolein with bromine and 
baryta water; 

3. By the action of dilute alkali on glycerose, which is 
formed by oxidation of glycerol. 

It will be observed that formic aldehyde has the same per- 
centage composition as fructose. It is the simplest possible 
compound to which the name carbohydrate can be applied. 

When acrolein is treated with bromine, two atoms of the 
latter are added directly to the former : — 

CH., CH.Hi 

I I 

CH +2Br = CHBr. 

I I 

ron COH 

When this dibroinide is treated with baryta water, hydroxy] 
is first substituted for bromine, ami glyceric aldehyde is the 
first product. This then is polymerised and forms i-fructose : - 



188 CARBOHYDRATES. 

CH 2 Br CH 9 0H 

! I 

CHBr + Ba(OH) 2 = CHOH + BaBr 2 ; 
I I 

COH COH 

CH.OH 

I 
2 CHOH = CgH^Oe. 

I 
COH 

On account of the formation of ?'-fructose from acrolein it 
was called acrose. It was later shown to be the inactive 
variety of fructose, and the name acrose became unnecessary, 
though it is still used. 

The formation of z-fructose from glycerose takes place as 
represented in the following equation : — 
CH 9 0H CH 2 OH 

I I 

CHOH + CO = CH 2 OH - CHOH - CHOH - CHOH - CO 

i | - CH 2 OH. 

CHO CH 2 OH 

The aldehyde group CHO reacts with one of the CH 2 OH 
groups of the ketone thus : — 

H H H H 

C = + CHOH = C - OH - COH. 

This reaction is known as the aldol condensation, because the 
product first obtained in this way was called aldol. This was 
formed by condensation of ordinary aldehyde thus : — 

CH 3 . CHO + CH 3 . CHO = CH 3 . CHOH . CH 2 .CHO. 

Aldol. 

Aldol is really /?-hydroxycrotonic aldehyde. 

When i-fructose is treated with yeast, it is partly trans- 
formed by the ferment into alcohol and carbon dioxide. It is 
the d-fructose contained in it that undergoes the change, while 
the Z-fructose remains behind unchanged, and can be obtained 
free from the other two varieties. 



FRUCTOSE. 189 

Constitution of glucose and fructose. — Two reactions have 
been of special value in the determination of the constitution 
of the members of the group of monosaccharides. 

a. When either an aldehyde or an acetone is treated with 
hydrocyanic acid an addition-product is formed thus : — 

H H 

1 ' OH 



CH 3 . C = + HCN = CH 3 . C < 



CN' 



and CH3 >c = + HCN = CH3 >c< OH 

The products can be converted into corresponding acids by the 
change of the cyanogen group into carboxyl. Thus the nitril 
from aldehyde yields a-hydroxypropionic (or lactic) . acid : — 

H H 

CH3.C<^+2H 2 = CH 3 .C<^ OH + NH 3 ; 

while the nitril from acetone yields a-hydroxyisobutyric acid : — 

CH 3 „ OH OTT ^ CIT, „ OH 

CH a > C < CN + 2 H2 ° = CH3 > C < COOH + NH » 

By the aid of these reactions it has been shown that glucose 
is an aldose, and fructose a ketose, of these formulas : — 

(1) CHO - CHOH - CHOH - CHOH - CHOH - CH.OH. 

Glucose. 

(2) CH 2 OH- CO -CHOH -CHOH- CHOH -CH 2 OH. 

Fructose. 

By adding hydrocyanic acid to a compound of formula ^H a 
nitril of the following formula would be formed : — 

HQ>CH- CHOH -CHOH -CHOH -CHOH --('11,011. 

This would yield ;iu acid of the formula: — 

HOOC 

no ►CH -CHOH -CHOH -CHOH -CHOH -CH OH. 



190 CARBOHYDRATES. 

By treating this with hydriodic acid it would be reduced to 
the acid : — 

X1O2C . CH2 . OrLj . CU2 • ^H-2 . CHo . CH 3 . 

The acid obtained from dextrose by means of the above re- 
actions has the structure represented by this formula, and it 
hence follows that dextrose itself must have the structure 
represented by formula (1) above, or it must be an aldose. 

By subjecting fructose to the same processes, the product 
obtained has the structure : — 

C0 2 H 
I 
CH 3 . CH . CH 2 . CH 2 . CH 2 . CH 3 ; 

and it follows from this that fructose must have the structure 
represented by formula (2) above, or it must be a ketose. 

b. When an aldehyde or an acetone is treated with phenyl- 
hydrazine, CeH5.JSrH.NH2, a reaction takes place, as represented 
in this equation : — 

H H 

I I 

E.C = + H 2 N.NHC 6 H 5 = E.C = N.NHC 6 H 5 + H 2 0. 

The products thus formed are called hydrazones. 
The sugars form hydrazones when treated with phenyl- 
hydrazine. Thus dextrose and fructose give the products 

(1) CH 2 OH.CHOH.CHOH.CHOH.CHOH.CH 

II 
N.NHC 6 H 5 . 

Hydrazone of Glucose. ° ° 

(2) CH 2 OH.CHOH.CHOH.CHOH.C.CH 2 OH 

II 
N.NHC 6 H 5 . 

Hydrazone of Fructose. 

If the sugars are boiled with an excess of phenylhydrazine a 
second reaction takes place. In the case of glucose, the CHOH 
group adjoining the carbon atom with which the residue of 



FRUCTOSE. 191 

phenylhydrazine is combined, is oxidized to the ketone group 
GO and then phenylhydrazine reacts with this in the usual 
way, the product being a compound of the formula — 

CH 2 OH - CHOH - CHOH - CHOH - C - CH 

II II 
C 6 H 5 HN . N N . NHC 6 H 5 . 

This is called an osazone or, specifically, glucosazone. 

In the case of fructose, the primary alcohol group, CH 2 OH, 
adjoining the carbon atom with which the residue of phenylhy- 
drazine is combined is oxidized to the aldehyde group, CHO, 
and then phenylhydrazine reacts with this in the usual way, 
giving a product of the formula — 

CH 2 OH . CHOH . CHOH . CHOH . C . CH 

II II 
C 6 H 5 HN.N N.NHC 6 H 5 . 

This is the osazone of fructose or fructosazone. Glucosa- 
zone and fructosazone are identical. 

The osazones are in general difficultly soluble in water and 
have characteristic properties whereby they can be recognized. 
The sugars themselves are easily soluble and it is hard to 
separate them, and until the discovery of the phenylhydrazine 
reaction the investigation of the sugars advanced very slowly. 
This reaction in the hands of one of the most skilful experi- 
menters has advanced our knowledge of the sugar group 
enormously within a few years past. 

The formation of the osazones makes it possible to recognize 
the different sugars, but it does not give the sugars themselves. 
The regeneration of the sugars from the osazones is of groat 
importance. The principal reactions available for this purpose 
are the following : — 

1. The osazone is heated for a short time with finning 
hydrochloric acid when it yields phenylhydrazine hydrochlo- 
ride ami an osone, thus: — 



192 CARBOHYDRATES. 

CH 2 OH . (CHOH) 3 . C . C -f 2 H 2 + 2 HC1 
II II 
C 6 H 5 HN.N N.NHC 6 H 5 

= CH 2 OH(CHOH) 3 CO . CHO + 2 C 6 H 5 . NH . NH 2 . HC1. 

Osone. 

2. The osone can be isolated and reduced by means of acetic 
acid and zinc dust, when it is converted into the corresponding 
ketose : — 

CH 2 OH(CHOH) 3 CO . CHO + 2H 

= CH 2 OH(CHOH) . CO. CH 2 OH. 

Whether the original sugar was an aldose or a ketose, the 
final product of the above series of reactions is a ketose. The 
aldoses cannot, therefore, be regenerated in this way. On the 
other hand, any aldose can be converted into a ketose by this 
means. 

Mannose, 6 H 12 O 6 . — cZ-Mannose is one of the products of 
oxidation of cZ-mannite, and is obtained by the action of dilute 
acids on some kinds of cellulose. The shavings formed in the 
manufacture of buttons from vegetable ivory are rich in the 
cellulose which yields d-mannose. 

J-Mannose and i-mannose have also been prepared. 

The mannoses are aldehydes, and are stereoisomers with 
glucose. 

Galactose, C 6 H 12 6 . — d-Galactose is formed by treatment 
of sugar of milk with dilute acids, c?-glucose being formed at 
the same time. Other carbohydrates also yield it. I- and 
^'-Galactoses are known. By reduction cl- and /-galactoses are 
transformed into dulcite. By oxidation all three galactoses 
yield mucic acid. 

Gulose, 6 H 12 O 6 . — The three guloses have been made arti- 
ficially. They are aldoses corresponding to the three sorbites, 
and are stereoisomers with the glucoses. 

The method by which Z-gulose was made is of special interest, 
as it is based upon reactions that may be used for passing from 



GULOSE. 193 

an aldose of a certain composition to one containing one carbon 
atom more. This method, as will be seen, makes it possible to 
pass from a pentose to a hexose, from a hexose to a heptose, 
etc. It consists in adding hydrocyanic acid to the aldose, con- 
verting the nitril thus obtained into the corresponding acid, 
and then reducing the acid. Thus in the case of £-gulose the 
starting-point is xylose, and the steps may be briefly represented 
thus : — 

Xylose ->- (addition of hydrocyanic acid) -> £-gulonic acid -> 
reduction -> Z-gulose. 

2. Polysaccharides or Complex Sugars. 

The polysaccharides, or complex sugars, are found in nature, 
as, for example, cane sugar and sugar of milk, or are formed 
from more complex carbohydrates, as, for example, maltose 
from starch. Their most characteristic property is their power 
to break down into monosaccharides under the influence of 
dilute acids or enzymes. The reaction involves the addition 
of the elements of water, and is called hydrolysis. A simple 
example of this kind of action is the conversion of maltose into 
d-glucose : — 

C 12 H 22 O n + H 2 = 2 CeHjA. 

Maltose. cZ-Gluoose. 

In most cases the hydrolysis of a polysaccharide gives more 
than one monosaccharide. Cane sugar, for example, gives 
(/-glucose and tf-fructose : — 

C 12 Il 22 O n + 1LO = C 6 H u 6 + C,,H,A; 

Cane Sugar, d-Gluoose. d-Fruotose, 

sugar of milk gives d-galactose and (/-glucose: — 
C^lUOn + H 2 = (\;I1,.0, + C.H.A- 

rf-Galaotose. tf-Gluoose. 

Polysaccharides that give two monosaccharides when hydro- 
lyzed are known as saccharobioses ; those that give three, as 
sacchctrotrioses. 



194 CARBOHYDRATES. 

Cane sugar, Saccharose, C 12 H220 n . — This well-known 
variety of sugar occurs very widely distributed in nature, in 
sugar cane, sorghum, the Java palm, the sugar maple, beets, 
madder root, coffee, walnuts, hazel nuts, sweet and bitter 
almonds ; in the blossoms of many plants ; in honey, etc., etc. 

It is obtained mainly from the sugar cane and from beets. 
In either case the processes of extraction and refining are largely 
mechanical. When sugar cane is used, this is macerated with 
water to dissolve the sugar. Thus a dark-colored solution is 
obtained. This is evaporated, and then passed through filters 
of bone-black which remove the coloring matter. The solu- 
tion is evaporated in the air to some extent, and then in 
large vessels called " vacuum pans," from which the air is 
partly exhausted, so that the boiling takes place at a lower 
temperature than would be required under the ordinary pres- 
sure of the atmosphere. The mixture of crystals and mother 
liquors obtained from the " vacuum pans " is freed from the 
liquid by being brought into the "centrifugals." These are 
funnel-shaped sieves which are revolved very rapidly, the liquid 
being thus thrown by centrifugal force through the openings of the 
sieve, while the crystals remain behind and are thus nearly dried. 
The final drying is effected by placing the crystals in a warm room. 

When beets are used, the process is essentially the same, 
though there are some differences in the details. 

The mother liquors which are obtained from the " centrifu- 
gals " are further evaporated, and yield lower grades of sugar ; 
and, finally, a syrup is obtained which does not crystallize. 
This is molasses. Molasses is sometimes brought into the 
market as such; sometimes, particularly when obtained from 
beet sugar, it is allowed to ferment for the purpose of making 
alcohol. The spent wash, or waste liquor, " vinasse," is now 
evaporated to dryness and calcined for the purpose of getting 
the alkaline salts contained in the residues. The products of 
distillation are collected, and from them tri-methyl-amine is 
separated (see p. 96). 



CANE SUGAR. 195 

Sugar crystallizes from water in well-formed, large mono- 
clinic prisms. It is dextro-rotatory. When heated to 210° to 
220°, cane sugar loses water, and is converted into the substance 
called caramel, which is more or less brown in color, according 
to the duration of the heating and the temperature reached. 
Boiled with dilute mineral acids, cane sugar is split into equal 
parts of glucose and fructose, as has been stated. The mix- 
ture of the two is called invert-sugar. The process is called 
inversion. It takes place, to some extent, when impure sugar 
is allowed to stand. Hence invert-sugar is contained in the 
brown sugars found in the market. The enzyme, invertin (see 
p. 184), formed by yeast, gradually transforms cane sugar into 
glucose and fructose, and these then undergo fermentation. 
Cane sugar itself does not ferment. 

Cane sugar does not reduce an alkaline solution of copper 
sulphate. If the two are boiled together for some time, the 
sugar is to some extent inverted, and to this extent reduction 
of the copper salt takes place. 

Experiment 39. Prepare a dilute solution of cane sugar by dis- 
solving Is to 2s in 200 cc water. Test this with Fehling's solution, 
as in Exp. 38. Now add to the sugar solution 10 drops concentrated 
hydrochloric acid, and heat for half an hour on the water-bath at 
100°; exactly neutralize the acid with a dilute solution of sodium 
carbonate, and test with Fehling's solution. 

Oxidizing agents readily convert cane sugar into oxalic acid 
(see Exp. 34) and saccharic acid. 

Like glucose, cane sugar forms compounds with metals, 
metallic oxides, and salts. Among these the following mav 
be mentioned : — 

Sodium sucrate .... (\.II..,(V.Na. 

Sodium-chloride sucrate . . (\.A I.-O,,. Nad, 

Calcium sucrate .... C,,.l I._vO u .Ca, 

and Lime sucrate (Ydl.-.O,, . 2 CaO. 

These derivatives arc not sweet. 



196 CARBOHYDRATES. 

An oct-acetate of the formula C 12 H 14 (C 2 H 3 0) 8 11 has been made 
by treating sugar with sodium acetate and acetic anhydride. 

Cane sugar is in some way made up by a combination of a 
molecule of d-glucose and a molecule of d-fructose, with elimi- 
nation of a molecule of water. The resulting compound does 
not react with phenylhydrazine nor with Fehling's solution, 
and, therefore, it probably does not contain a carbonyl group 
CO. The artificial preparation of cane sugar from d-glucose 
and d-f ructose has not been effected. 

Sugar of milk, lactose, C 12 IL 22 O n + H 2 0. — This sugar oc- 
curs in the milk of all mammals, and is obtained in the manu- 
facture of cheese. The casein is separated from the milk by 
means of rennet ; the sugar of milk remains in solution, is 
separated by evaporation, and purified by recrystallization. It 
crystallizes in rhombic crystals. That which comes into the 
market has been crystallized on strings or wood splinters. It 
has a slightly sweet taste ; is much less soluble in water than 
cane sugar, and is dextro-rotatory. It reduces Fehling's solu- 
tion. Oxidized with nitric acid, it yields mucic and saccharic 
acids. Nascent hydrogen converts sugar of milk into mannite, 
dulcite, and other substances. Like glucose and cane sugar, 
it forms compounds with bases, dissolving lime, baryta, lead 
oxide, etc. 

Sugar of milk ferments under certain circumstances, and 
is thus converted into lactic acid. The souring of milk is a 
result of this fermentation. The lactic acid formed coagulates 
the casein ; hence the thickening. 

Maltose, C12H22O11. — This carbohydrate is formed by the 
action of malt on starch. Malt, which is made by steeping 
barley in water until it germinates, and then drying it, contains 
a substance called diastase, which has the power of effecting 
changes similar to some of those effected by the ferments. 
Thus, it acts upon starch, and converts it into dextrin and 
maltose : — > 



CELLULOSE. 197 

3 C 6 H 10 O 5 + H 2 = C 12 H 22 O n -f C 6 H 10 O 5 . 

Starch. Maltose. Dextrin. 

Maltose is also formed by the action of dilute sulphuric acid 
upon starch, and is hence contained in commercial glucoses. 
By further treatment with sulphuric acid it is converted into 
glucose. Maltose crystallizes in fine needles; is dextro-rota- 
tory; reduces Fehling's solution, and ferments with yeast, it 
being first converted into monosaccharides by maltase, which 
is an enzyme contained in, or formed by, yeast. 

3. Polysaccharides, not Resembling Sugars. 

Cellulose, (CeHioOs^. — Cellulose forms the groundwork 
of all vegetable tissues. It presents different appearances 
and different properties, according to the source from which it 
is obtained ; but these differences are due to substances with 
which the cellulose is mixed; and when they are removed, 
the cellulose left behind is the same thing, no matter what 
its source may have been. The coarse wood of trees, as well 
as the tender shoots of the most delicate plants, all contain 
cellulose as an essential constituent. It forms the membrane 
of the cells. Cotton-wool, hemp, and flax consist almost 
wholly of cellulose. 

For the preparation of cellulose, either Swedish filter-paper 
or cotton- wool may be taken. 

Experiment 40. Treat some cotton-wool successively with ether, 
alcohol, water, a caustic alkali, and, finally, a dilute acid. Then wash 
with water. 

Cellulose is amorphous ; insoluble in all ordinary solvents ; 
soluble in an ammoniacal solution of oupric oxide. It dis- 
solves in concentrated sulphuric acid. If the solution is 
diluted and boiled, the cellulose is converted into dextrin 
and glucose. U will thus be seen that rags, paper, and 
wood, which consist, largely of cellulose, might be used for 
the preparation of glucose, and consequently of alcohol, 



198 CARBOHYDRATES. 

Experiment 41. Dissolve a sheet or two of filter-paper in as small 
a quantity of concentrated sulphuric acid as will suffice ; dilute with 
water to about half to three-quarters of a litre, and boil for an hour. 
Remove the sulphuric acid by means of chalk ; filter ; evaporate ; and 
test for glucose by means of Eehling's solution. 

Gun cotton, pyroxylin, nitro-cellulose. — Cellulose has 
some of the properties of alcohols ; among them the power to 
form ethereal salts with acids. Thus, when treated with nitric 
acid, it forms several nitrates, just as glycerol forms the nitrates 
known as nitro-glycerin (which see). 

When cotton is exposed for some time to the action of a 
warm mixture of nitre and sulphuric acid, soluble cotton or 
soluble pyroxylin is formed. This consists of the lower nitrates 
(the di-, tri-, and tetra-nitrates), which are soluble in ether 
containing a little alcohol. 

The solution is called collodion solution. When poured upon 
the surface of a solid, such as glass, the ether and alcohol 
rapidly evaporate and leave a thin coating of the nitrates. It 
finds extensive application in surgery and in photography. 

When treated with a mixture of nitric and sulphuric acids, 
cotton yields the higher nitrates (tetra-, penta-, and hexa- 
nitrates). These are called gun cotton or pyroxylin. They are 
extensively used as explosives. Gun cotton forms the active 
constituent of some of the smokeless powders now so exten- 
sively used. In the manufacture of these powders the gun 
cotton is gelatinized by treating it, in finely divided condition, 
with acetone or some other similar solvent. Under these cir- 
cumstances the gun cotton does not dissolve, but it swells up 
and forms a gelatinous mass. From this the solvent is removed 
by pressure and evaporation, and the residual mass cut into 
laminae, or powdered by appropriate methods. The name " ex- 
plosive gelatin " is given to the substance prepared as above. 

A solution of soluble cotton in molten camphor gives celluloid. 
As it is plastic at a slightly elevated temperature, it can easily 
be moulded into any desired shape. When it cools it hardens. 



STARCH. 199 

Paper. — Paper in its many forms consists mainly of cellu- 
lose. The essential features in the manufacture of paper are, 
first, the disintegration of the substances used. This is effected 
partly mechanically, and partly by boiling with caustic soda. 
The mass is converted into pulp by means of knives placed on 
rollers. The pulp, with the necessary quantity of water, is 
then passed between rollers. Chiefly rags of cotton or linen are 
used in the manufacture of paper ; wood and straw are also used. 

Starch, (C 6 H 10 O 5 ) x . — Starch is found everywhere in the vege- 
table kingdom in large quantity, particularly in all kinds of 
grain, as maize, wheat, etc. ; in tubers, as the potato, arrow- 
root, etc. ; in fruits, as chestnuts, acorns, etc. 

In the United States starch is manufactured mainly from 
maize ; in Europe, from potatoes. 

The processes involved in the manufacture of starch are 
mostly mechanical. The maize is first treated with warm 
water; the softened grain is then ground between stones, a 
stream of water running continuously into the mill. The thin 
milky fluid which is carried away is brought upon sieves of silk 
bolting-cloth, which are kept in constant motion. The starch 
passes through with the water as a milky fluid, and this is 
allowed to settle when the water is drawn off. The starch is 
next treated with water containing a little alkali (caustic soda, 
or sodium carbonate), the object of which is to dissolve gluten. 
oil, etc. The mixture is now brought into shallow, long wooden 
runs, where the starch is deposited, the alkaline water running 
off. Finally, the starch is washed with water, and dried at a 
low temperature. 

Starch has a granular structure, the grains as seen under the 
microscope having a series of concentric markings, the nucleus 
of which is at one side. 

Starch in its usual condition is insoluble in water. It" ground 
with cold water, i t is partly dissolved. It' heated with water, 
the membranes of the starch-cells are broken, ami the contents 



200 CARBOHYDRATES. 

form a partial solution. On cooling, it forms a jelly called 
starch paste. 

With iodine, starch paste gives a deep blue color ; with bro- 
mine, a yellow color. 

Experiment 42. Make some starch paste thus : Put a few grams 
of starch 1 in an evaporating dish ; pour enough cold water upon it to 
cover it ; grind it under the water with a pestle, and then pour 200 cc to 
300 cc hot water upon it. When this is cool, add a few drops to a litre 
of water, and then add a few drops of potassium iodide. As long as 
the iodine is in combination with the potassium no change of color 
takes place ; but if the iodine is set free by the addition of a drop or 
two of chlorine water, or of strong nitric acid, the entire liquid turns 
a beautiful dark blue. The cause of this color is the formation of a 
very unstable compound of starch and iodine. The color is easily 
destroyed by a slight excess of chlorine water (try it in a test-tube) ; 
by alkalies (try it) ; by sulphurous acid (try it) ; by hydrogen sulphide 
(try it) ; etc. It is also destroyed by heating. (Heat some of the solu- 
tion in a test-tube, and let it stand.) The color reappears on cooling. 

Experiment 43. Use some of the starch paste in studying the effect 
of bromine upon it. Use dilute solutions. The bromine must be in the 
free condition. 

Starch is converted into dextrin, maltose, and glucose by 
dilute acids ; diastase converts it into maltose and dextrin. 

Experiment 44. Add 20 cc concentrated hydrochloric acid to 200 cc 
of the starch paste already made, and heat for two hours on the water- 
bath, connecting the flask with an inverted condenser (see Fig. 8). 
Then examine with Fehling's solution. Test, also, some of the original 
starch paste with Fehling's solution. 

When starch is treated for a few days with cold, dilute 
mineral acids, it is converted into "soluble starch," which 
dissolves in water without the formation of a paste. 

Glycogen, {C^KJd^)^ This is a carbohydrate resembling 
starch that occurs in the animal organism. It is found in 

1 The purest form of starch to be found in the market is that made from arrow-root. 
Ordinary starch contains other substances which sometimes interfere with the reactions. 



GUMS. 201 

the muscles, but disappears during exercise or hunger. It is 
especially abundant in the liver of healthy animals. It yields 
dextrin, maltose, and d-glucose when hydrolysed. 

Dextrin, C 6 H 10 O 5 . — Dextrin is formed by treating starch 
with dilute acids or diastase. It is converted by further treat- 
ment with acids into glucose. The substance ordinarily called 
dextrin has been shown to be a mixture of several isomeric sub- 
stances which resemble each other very closely. The mixture 
is an uncrystallizable solid. It is strongly dextro-rotatory ; 
gives a red color with iodine, and does not reduce Fehling's 
solution. It is used extensively as a substitute for gum. 

Gums. — Under this head are included a number of sub- 
stances which occur in nature. One of the best known is grim 
arable, which is obtained in Senegambia from the bark of trees 
belonging to the Acacia variety. Its formula, like that of cane 
sugar, is C^H^Ou. Other gums are ivood gum, obtained from 
the birch, ash, beech, etc. ; bassorin, the chief constituent of 
gum tragacanth, etc. 

Our knowledge of the chemistry of these gums is very limited. 



CHAPTEE XII. 

MIXED COMPOUNDS CONTAINING NITROGEN. 

In speaking of the preparation of dibasic acids from mono- 
basic acids, reference was made to cyan-acetic and the two 
cyan-propionic acids. These are nothing but simple cyanogen 
substitution-products analogous to chlor-acetic and the two 
chlor-propionic acids. They are made by treating the chlorine 
products with potassium cyanide. They have been useful 
chiefly in the preparation of dibasic acids, as described in con- 
nection with malonic and the two succinic acids. It will there- 
fore not be necessary to consider them individually here. 

Note for Student. — How can malonic be made from acetic acid ; 
and the two succinic acids from propionic acid ? Give the equations. 

The chief substances to be considered under the head of 
mixed compounds containing nitrogen are the amino-acids and 
the acid amides. As will be seen, both, these classes of sub- 
stances are of special interest, as they represent forms of com- 
bination which are favorite ones in nature, especially in the 
animal kingdom, some of the most important substances found 
in the animal body, such as urea, uric acid, glycocoll, etc., 
belonging to one or both the classes. 

Amino-acids. 

The relation of an amino-acid to the simple acid is, as the 
name implies, the same as that of an amino derivative of a 
hydrocarbon to the hydrocarbon. That is to say, it may be 
regarded as the acid in which a hydrogen is replaced by the 
amino group, NH 2 . Thus, amino-acetic acid is represented 



■L , 



AMINO-FORMIC ACID. 203 

by the formula CH 2 < r0 2 H ; while amino-methane, or methyl- 

amine is represented thus, CH 3 .NH 2 . The reasons for regard- 
ing methyl-am ine as a substituted ammonia, as represented, 
have been stated. The formula is based upon the reactions 
of the substance ; that is, upon its chemical conduct and the 
methods used in its preparation. The same arguments lead 
in the same way to the view that the ammo-acids are 
substituted ammonias, and, at the same time, acids. The 
simplest method for their preparation consists in treating 
halogen derivatives of the acids with ammonia; thus amino- 
acetic acid can be made by treating brom -acetic acid with 
ammonia : — 

Note for Student. — Compare this reaction with that made use of 
for making methyl-amine. 

NH2 
Amino-formic acid, carbamic acid, 1 . — This acid 

CO.H 

is not known in the free condition. Its animoniuin salt, 

NH 2 

I , is formed when carbon dioxide and ammonia are 

C0 2 NH 4 

brought together, and it is therefore contained in commercial 
ammonium carbonate : — 

NH.> 

I 

The other carbamates are prepared from the ammonium 
salt. They are decomposed, yielding carbonates and ammonia. 
Thus, when potassium carbamate is warmed in water solution, 
decomposition takes place, as represented in the equation, — 

N1L..CO..K + H 8 = NH 8 + HKC08. 

The ethereal salts oi' earbamie acid, called tort/lanes, are 



204 MIXED COMPOUNDS CONTAINING NITROGEN. 

readily made by treating the ethereal salts of chlor-formic acid 
(see p. 157) with ammonia : — 

CI NH 2 

I I 

C0 2 C 2 H 5 + 2 NH 3 = C0 2 C 2 H 5 + KH 4 C1. 

Amino-formic acid cannot be taken as a fair representative 
of the ammo-acids, any more than carbonic acid can be taken 
as a fair representative of the hydroxy-acids. 

Glycocoll, glycine, | / = NH, \ _ In &e 

amino-acetic acid, i V C0 2 H/ 

bile are contained two complicated acids, which are known as 
glycocholic and taurocholic acids. When glycocholic acid is 
boiled with hydrochloric acid, it breaks np, yielding cholic acid 
and glycocoll. In the' urine of horses is found an acid known 
as hippuric acid. When this is boiled with hydrochloric acid, 
it breaks up into benzoic acid and glycocoll. 

When uric acid is treated with hydriodic acid, glycocoll is 
one of the products. Further, glycocoll is formed when glue is 
boiled with baryta water or dilute sulphuric acid. Its formation 
from brom-acetic acid and ammonia, mentioned above, gives 
the clearest indication in regard to its relation to acetic acid. 

Amino-acetic acid is soluble in water, insoluble in alcohol or 
ether. It has a sweetish taste, and is sometimes called gelatin 
sugar. 

Amino-acetic acid has both acid and basic properties. It 
unites with acids, forming weak salts ; and it acts upon bases, 
giving salts with metals, — the amino-acetates. It also unites 
with salts, forming double compounds. 

Examples of the compounds with acids are the 

Hydrochloride. . . . CH 2 <^JL HC1 , ' 

C0 2 H 

and the Nitrate CH 2 < ;! 3 ; 

C0 2 H 

of the salts with metals, 



SARCOSLNE. 205 

Zinc amino-acetate . . Zn(C 2 H 4 lSr0 2 ) 2 + H 2 0, 
and Copper amino-acetate . Cu(C 2 H 4 ]Sr02)2 4- H 2 ; 

of the compounds with salts, the double salt of 

Copper nitrate ) ~ „^ \ r (C Vf isio \ _l 9 TT O 

and Copper amino-acetate, j ^ 3 ' 2 ° 2 4 2 ' 2 

Treated with nitrous acid, glycocoll is converted into hydroxy- 
acetic acid. With soda-lime it gives methylamine. 

Note for Student. — Write the equation representing the reaction 
which takes place when glycocoll is treated with nitrous acid. 

It seems probable that amino-acetic acid and other similar 
compounds are really salts formed by the union of the acid con- 
stituent, carboxyl, with the basic constituent, ISTEU. In accord- 
ance with this view the formula should be written thus : — 

Sarcosine, methyl-glycocoll, 3 H 7 NO 2 ( =CH,< _,_ __ 
NH,,CH, ^ ° OJI 



/ 



or CH 2 <^ yo J. — When brom-acetic acid is treated with 

CO J 

methyl-amine instead of with ammonia, a reaction takes place 
similar to that which takes place with ammonia, the product 
being methyl-glycocoll or sarcosine : — 

CH 2 < ^ + 2 CH, . NIL = CI L < ™^ ( U ' + NH 3 (CH 8 ) Br. 

S:nvt>siiu\ 

Sarcosine is a product of the decomposition of creatine, which 
is found in flesh, and of caffeine, which is a constituent of coffee 
and tea. It is obtained from creatine and caffeine by boiling 
them with baryta water. Its properties are much like these 
of glycocoll. 

Amino-propionic acids, C :; H : NO., — These acids bear to 
propionic acid relations similar to that which ammo-acetic acid 



206 MIXED COMPOUNDS CONTAINING NITROGEN. 

bears to acetic acid. There are two, corresponding to a- and 
/?-chlor-propionic acids, from which they are made. They are 
not found in nature. Their properties are much like those of 
glycocoll. a- Amino-propionic acid is also called alanin. 

Note for Student. — What substances would be formed by treat- 
ing the two amino-propionic acids with nitrous acids ? 

Cystine, C 6 H 12 N 2 4 S 2 , a substance that is sometimes found 
as a crystalline sediment in the urine of human beings and dogs, 
is a derivative of a-amino-propionic acid. Tin and hydrochloric 
acid reduce it to cystein, C 3 H 7 N0 2 S. The two substances bear 
to each other the relations represented by these formulas : — 

r NH »>0 ^NH 3 H 3 N 1 

CH 3 .d CO >U CH 3 .C< C o >0 0< OC lc.CH 3 . 

I SH I- S S J 

Cystein. Cystine. 

Among the amino derivatives of the higher members of the 
fatty acid series, that of caproic acid should be specially men- 
tioned. 

NH 
Leucine, C 5 H 10 < _ 3 > O, is a substance that is found 
GO 

widely distributed in small quantities in the animal organism 
in the glands and also in the sprouts of plants. It is also 
formed by the decomposition of albumins and gelatin. It is 
probable that there are different leucines. Artificially prepared 
a-amino-caproic acid, CH 3 . CH 2 . CH 2 . CH 2 . CH(NH 2 ) . C0 2 H, 
appears to be identical with the leucine obtained from casein ; 
while that obtained from vegetable albumin, from glue and horn, 
is a-amino-isobutylacetic acid, (CH 3 ) 2 CH . CH 2 . CH(!S'H 2 ) . C0 2 H. 
Leucine is evidently of great physiological importance. 

Amino-sulphonic Acids. 

Just as there are amino derivatives of the carbonic acids, 
so, too, there are amino derivatives of the sulphonic acids. 
The most important of these is 



AMINO-DIBASIO ACIDS. 207 

Taurine, }c,H ; NS0 3 f =C 2 H 4 <^°! H 

p- Ammo-ethyl-sulphonic acid,i \ NH 2 

Taurine is found in combination with cholic acid in taurocholic 

acid, in ox bile, and the bile of many animals, as well as in 

other animal liquids. It has been made synthetically from 

ATT 

isethionic acid, C 2 H 4 < , by treating the acid successively 

with phosphorus pentachloride and ammonia : — 

C 2 H 4 < ^ QH + 2 PC1 5 = C 2 H 4 < ^ C1 + 2 POCl 3 + 2 HC1 ; 

Isethionic acid. Chlor-etkyl-sulphon-chloride. 

CI CI 

C2H4< S0 2 C1 +H2 ° =C2H ' < S0 2 OH + HC1; 

Chlor-ethyl-sulphonic acid. 

C 2 H 4 < ^ 0H + 2NH S = C 2 H 4 < jjjj^. + NH 4 C1. 

Taurine. 

Taurine crystallizes in large monoclinic prisms. It is a very 
stable substance, and can be boiled with concentrated acids with- 
out decomposition. With nitrous acids it yields isethionic acid. 

It unites with strong bases forming salts, but not with acids. 
This conduct is in accordance with the view that taurine is an 

ammonium salt as represented by the formula, C2II4 < D 3 > 0. 

Amtno-dibasic Acids. 
Aspartic acid, J / = CH(NH)< CO.H 

Amino-succinic acid, ) \ v _/ CO s H 

CH(NH.,) . CO.,H 

or I 

CH,.CO,II. 

Aspartic acid occurs in pumpkin seeds, and is frequently met 
with as a product of boiling various natural compounds with 
dilute acids. Thus, for example, it is formed when casern and 
albumin arc treated m this way, It is formed also when 
asparaginic (which sec) is boiled with acids or alkalies. 



208 MIXED COMPOUNDS CONTAINING NITROGEN. 

Aspartic acid crystallizes in rhombic prisms, which are diffi- 
cultly soluble in water. The solution of the natural product 
is levo-rotatory. It contains an asymmetric carbon atom, and 
the three varieties (cl-, 1-, and i-) suggested by the theory are 
known. When each of the varieties is treated with nitrous 
acid it is converted into the corresponding malic acid. 

Acid Amides. 

When the ammonium salt of acetic acid is heated, it gives off 
water, and a body distils over which is known as acetamide. 
The reaction is represented by the following equation : — 

CH 3 . COONH 4 = CH 3 . CONH 2 + H 2 0. 

The substance obtained has neither acid nor basic properties. 
An examination of the ammonium salts of other acids that 
contain carboxyl shows that the reaction is a general one, and 
a class of neutral bodies, known as the acid amides, can thus 
be obtained. As no one of the acid amides of the fatty acid 
series is of special importance, a few words of a general char- 
acter in regard to the class will suffice. 

Besides the reaction above given, there are two others of 
general application for the preparation of the acid amides. 
One consists in treating an ethereal salt of an acid with am- 
monia ; thus, when ethyl acetate is treated with ammonia, this 
reaction takes place : — 

CH 3 . C0 2 C 2 H 5 + NH 3 = CH 3 . CONH 2 + C 2 H 6 0. 

The other reaction consists in treating the acid chlorides with 
ammonia. Thus, to get acetamide, we may treat acetyl chloride 
(see p. 61) with ammonia : — 

CH 3 . COC1 + 2 NH 3 = CH 3 . CONH 2 + NH 4 C1. 

This last reaction is perhaps most frequently used. It shows 
the relation that exists between acetic acid and acetamide. 
For acetyl chloride is made from acetic acid by treatment with 



ACID AMIDES. 209 

phosphorus trichloride, and is, therefore, as has been pointed 
out, to be regarded as acetic acid in which the hydroxyl is 
replaced by chlorine. Now, by treatment with ammonia the 
same reaction takes place as that which we have had to deal 
with in the preparation of amino-acids ; the chlorine is replaced 
by the amino group. Therefore, acetamide is acetic acid in 
which the hydroxyl is replaced by the amino group, as shown 
in the formulas : — 



II II 

CH 3 • C-OH CH 3 -C-NH 2 . 

Acetic acid. Acetamide. 

As the acid hydrogen of the acid is replaced, the amide is not 
an acid. On the other hand, the basic properties of the am- 
monia are destroyed by the presence of the acid residue as a 
part of its composition. This latter fact may be stated in 
another way ; viz., when an ammonia residue is in combination 
with carbon, which in turn is in combination with oxygen, its 
basic properties are destroyed. 

The amides are converted into ammonia and a salt when 
boiled with strong bases : — 

CH 3 • CONPL + KOH = CH 3 C0 2 K + NE, 

They are converted into cyanides by treatment with phos- 
phorus pentoxide, P 2 O s : — 

CH ;? • CONH 2 = CH, • iN + H.,#. 

As the substance obtained in this way is identical with methyl 
cyanide, which is formed by treating methyl-sulphuric acid with 
potassium cyanide, the reaction furnishes additional evidence 
in favor of the conclusion already reached; viz., that in the 
cyanides the carbon and not the nitrogen oi' the cyanogen 
group is in combination with the hydrocarbon residue, as repre- 
sented in the formula. OIL N. 

As the amide can be made from the ammonium salt and 
the cyanide or nitril from the amide, so, by starting with the 



210 



MIXED COMPOUNDS CONTAINING NITROGEN. 



cyanide, the amide and the ammonium salt can be made. The 
reaction by which the cyanides are converted into acids is based 
upon these relations. We have : — 

E . COONH 4 ->- E . CONH 2 ->- E . CN, 

and E • CN -^ E . CONH 2 ->- E . COONH 4 . 

As acetamide is made by treating ammonia with the chloride 
of acetic acid, so, by treating ammonia with the chloride of any 
acid, the corresponding amide can be made. So, also, by treat- 
ing ammonia with acid chlorides, or by treating acid amides 
with strong acids, more complicated compounds can be obtained. 

c C 2 H 3 
-acetamide, N-j C 2 H 3 0, 

I C0H3O 

may serve as examples. The relations of these substances to 
ammonia and to acetic acid are shown by the formulas, ordinary 
or mon-acetamide being NH 2 . C 2 H 3 or CH 3 . CO . NH 2 . 



C 2 H s O 



Of these di-acetamide, NH<[ ^ 2ri3 ^, and tr 

lC 2 H 3 0' 




Fisr. 12. 



Experiment 45. Arrange an apparatus as shown in Fig. 12. In 
flask A put 50s oxalic acid (dehydrated at 100°) and 50- absolute alco- 
hol ; and, in flask B, 50? absolute alcohol. Heat the bath D to 100° ; 
and then heat the alcohol in flask B to boiling, and continue to pass 



ASPARAGINE. 211 

the vapor from flask B into the mixture in flask A, meanwhile allowing 
the temperature of the oil-bath to rise to 125°-130°. A mixture of alcohol 
and ethyl oxalate will distil over, while the ethyl oxalate will be mostly 
in flask A. Add concentrated ammonia to some of the ethyl oxalate. 
Oxamide is thrown down as a white powder. What reactions have taken 
place ? Write the equations. Filter off the oxamide, and wash it with 
water. See whether it conducts itself like an acid. Has it an acid 
reaction ? Boil with caustic potash (not too much), and notice whether 
ammonia is given off. Why does it dissolve ? How can the oxalic acid 
be extracted from the solution ? 

When the amide of a poly-basic acid is boiled with ammo- 
nia, and under some other circumstances, partial decomposition 
takes place, and a substance is formed which is both amide 
and acid. Thus, in the case of oxamide, the product is oxamic 

C0 2 H 
acid, i . This acid forms well-characterized salts and 

CONH 2 

other derivatives such as are obtained from acids in general. 
There is one acid of this kind which is a well-known natural 
substance. It has already been referred to in connection with 
aspartic acid, which is closely related to it. It is 

Asparagine, amino-succinamic acid, 

/OH 3 • CONH \ 
C4H8N2O3+H2O 1 . — Asparagine is found 

\CH(NH,<).COOH/ 

in many plants, as in asparagus, liquorice, beets, peas, beans, 

vetches, and in wheat. It can be made by treating moii- 

ethyl amino-succinate with ammonia. 

Note for Student. — What reaction takes place? Write the equa- 
tion. 

Asparagine forms largo rhombic crystals, difficultly soluble 
in cold water, more easily in hot water. When boiled with 
acids or alkalies, it is converted into aspartic acid and ammonia. 

Norn fob Student. — Not iee that only the amino group of the amide 
is driven out of the compound by this treatment. The other amino 
group whioh is contained in the hydrocarbon portion of the compound 

is not affected. 



212 MIXED COMPOUNDS CONTAINING NITBOGEN. 

Nitrous acid converts asparagine into malic acid. 

Asparagine contains an asymmetric carbon atom, and two of 
the three theoretically possible stereoisomeric varieties are 
known. The levo-rotatory variety is found in the seeds of 
many plants, in asparagus, in beets, in peas, beans, and hi 
vetch sprouts. The dextro-variety is also found in vetch 
sprouts. The inactive variety is not formed when the two 
active varieties are brought together in solution. 

CO 

Succinimide, C2H4<p >NH. — This compound deserves 

attention in this connection, as it represents a not uncommon 
class known as the acid imides. They are formed from poly- 
basic acids, most simply from dibasic acids. They may be 
regarded as the anhydrides in which the imino group has 
been substituted for an oxygen atom. They are formed from 
the amides by loss of ammonia. Thus : — 



CH 2 .COKH 2 


CH 2 .CO v 
= | >NH + NH 3 . 
CH 2 .CCK 


1 


CH 2 .CONH 2 


Succinamide. 


Succinimide. 



The hydrogen atom of the imide is replaceable to some 
extent by metals, or the imide has the properties of a weak 
acid. 

Cyan-amides, CN2H2. — In speaking of cyanic acid, the 
existence of two chlorides of cyanogen was mentioned: one 
a liquid, having the formula NCC1 ; the other a solid, of the 
formula N 3 C 3 C1 3 . When the former is treated with ammonia, 
it is converted into an amide, NC . NH 2 , which bears to cyanic 
acid, NC . OH, the relation of an amide. Like the other simple 
compounds of cyanogen, cyan-amide readily undergoes change. 
When simply kept unmolested, it is converted into di-cyan- 
diamide, C 2 1S!" 4 H 4 ; while, when heated to 150°, a violent reaction 
takes place, and tri-cyan-triamide, C 3 N 6 H 6 , is formed. The 
latter compound is also called melamine and cyanuramide, and 
from certain methods of formation it is concluded that it is 



CREATININE. 213 

the amide of cyanuric acid. It is a strong mon-acid base. 
The formation of these compounds is particularly interesting, 
as illustrating the tendency on the part of the simpler cyanides 
to undergo change under slight provocation. 

Guanidine, CN3H5. — This substance, which is closely re- 
lated to cyan-amide, is formed by the oxidation of guanine 
(which see), and this in turn is obtained from guano. It can 
also be made by treating cyanogen iodide with ammonia : — 

NCI + 2NH 3 = (KH)C<^ m , 

the product being the hydriodic acid salt of guanidine. As 
will be seen, guanidine is cyan-amide plus ammonia : — 

NC . NH 2 + NH 3 = (NH)C < ^ 2 - 

JN xl 2 

It is a strongly alkaline base. Boiled with dilute sulphuric 
acid or baryta water, it yields urea and ammonia : — 

CN 3 H 5 + H 2 = CON,H 4 + NH 3 . 

Guanidine. Urea. 

Creatine, C4H9N3O2. — This substance is found in the 
muscles of all animals. It is closely related to guanidine and 
also to sarcosine (see p. 205). It has been made synthetically 
by bringing cyan-amide and sarcosine together. The reaction 
which takes place is analogous to that made use of for the 
preparation of guanidine : 

HN . CH, /NE, 

I =HN = C< , 



NseC-NH,+ I = HN = (\ clLiC00IL 



CH a 

Cyan-amide. Sarcosine. Creatine, 

Creatinine, CiHtN.O-, is in small quantity a constant con- 
stituent of urine. It can be made from creatine by evap- 
orating its solutions, especially it" aeids are present In 

contact with alkalies it. gradually takes up the elements of 



214 MIXED COMPOUNDS CONTAINING NITROGEN. 

water and forms creatine. It is a strong base, forming with, 
acids well crystallized salts. Its relation to creatine is repre- 
sented thus : — 

/NH 2 ,M 

HN = C< ^ TT „ AATT HN = C 



\ N CH 2 . COOH — _V/ \ N CH 2 . CO' 

CH 3 CH 3 

Creatine. Creatinine. 

Urea, or carbamide and derivatives. — Closely related 
to the nitrogen compounds just considered is urea, or the 
amide of carbonic acid. Its importance and certain peculiari- 
ties distinguish it from the other acid amides, and it is there- 
fore treated of by itself. 

Urea is found in the urine and blood of all mammals, and 
particularly in the urine of carnivorous animals. Human 
urine contains from 2 to 3 per cent ; the quantity given off by 
an adult man in 24 hours being about 30 g . Urea can be made 
by the following methods : — 

(1) By treating carbonyl chloride with ammonia : — 

COCl 2 + 2 NH 3 = CON 2 H 4 + 2 HC1. 
What is the analogous reaction for the preparation of acetamide ? 

(2) By heating ammonium carbamate : — 

CO< ONH =CON A + H 2 0. 
What is the analogous reaction for preparing oxamide ? 

(3) By treating ethyl carbonate with ammonia : — 

C0 < ^n 2 S 5 + 2 NH 3 = CON 2 H 4 + 2 C 2 H 6 0. 
UC 2 rl 5 

(4) By the addition of water to cyan-amide : — 

CN . NH 2 + H 2 = CON 2 H 4 . 

(5) By evaporation of ammonium cyanate in aqueous solu- 
tion : — 

CN(ONH 4 ) = CO]Sr 2 H 4 . 



UREA. 215 

This reaction is of special interest, for the reason that it 
afforded the first example of the formation, by artificial methods 
from inorganic substances, of an organic compound found in 
the animal body (see p. 1). 

Urea is most readily obtained from urine. 

Experiment 46. Evaporate four or five litres fresh urine to a thin, 
syrupy consistence. After cooling add ordinary concentrated nitric acid, 
when crystals of urea nitrate are obtained. Eilter, wash, and recrys- 
tallize from moderately concentrated nitric acid. When the crystals of 
urea nitrate are white, dissolve again in water, and add finely-powdered 
barium carbonate. The nitric acid forms barium nitrate, and the urea is 
left in free condition. Evaporate to dryness, and from the residue extract 
the urea with strong alcohol. 

Experiment 47. Make potassium cyan ate as directed in Experi- 
ments 24, p. 82, and 26, p. 84. Extract the cyanate with cold water, and 
add a solution of ammonium sulphate containing as much of the salt 
as there was used of potassium ferrocyanide in the preparation of the 
cyanate. Evaporate to a small volume, and allow to cool. Potassium 
sulphate will crystallize out. Filter this off, and evaporate to dryness. 
Extract with alcohol. The urea will crystallize from the alcoholic solu- 
tion when it is brought to the proper concentration. Give all the reactions 
involved in passing from potassium ferrocyanide to urea. Compare the 
urea made artificially with that made from urine. 

Urea crystallizes from alcohol in large rhombic prisms, 
which melt at 132°. 

Experiment 48. Determine the melting-points of both the natural 
and artificial specimens of urea. 

Urea is easily soluble in water and alcohol. Heated with 
water in a sealed tube to 100°, or boiled with dilute acid or 
alkalies, it breaks up into carbon dioxide and ammonia: — 

CON.,H 4 + 11,0 = CO, + 2 N II,. 

The same decomposition of the urea takes place spontaneously 
when urine is allowed to stand. Hence the odor o\' ammonia 
is always noticed in the neighborhood oi' urinals which are not 
kept thoroughly clean. This decomposition is due to the action 



216 MIXED COMPOUNDS CONTAINING NITROGEN. 

of an organism known as micrococcus ureal. This change is a 
good example of the way in which nature converts useless 
material into useful ones, Urea is a waste-product of the life- 
process. After it has left the body it ceases to be of value, 
whereas carbon dioxide and ammonia are of importance for 
the life of plants and animals. 

Sodium hypochlorite or hypobromite decomposes urea into 
carbon dioxide, nitrogen, and water. 

CO(N 2 H 4 ) + 3 NaOCl = C0 2 + 3 NaCl + N 2 + 2 H 2 0. 

The carbon dioxide can be measured by causing it to be 
absorbed in a solution of caustic potash, and from the amount 
formed the amount of urea decomposed can be determined. 
This is the basis of one of the methods used for estimating 
urea. 

Experiment 49. To a solution of 20s sodium hydroxide in 100 cc 
water add about 5 CC bromine, and shake well. Make a solution of urea 
in water, and add to the solution of the hypobromite. An evolution of 
gas will be noticed, showing that the urea is decomposed. 

Nitrous acid acts in the same way : — 

CON 2 H 4 + 2 HN0 2 = C0 2 + 2 N 2 + 3 H 2 0. 

When heated, urea loses ammonia, and yields first biuret, 
and finally cyanuric acid (see p. 85): — 



NH 2 NH 

og< mh; oc< atu , ATX t 

'NTT ! = NH +NH s 

NH 2 NH 2 

Urea. Biuret, 

3 CO(NH 2 ) 2 = C3H3O3N3 + 3 NH 3 . 

Cyanuric acid. 

Urea unites with acids, bases, and salts. The hydrogen of 
the amino groups can be replaced by acid or alcohol radicals, 

giving compounds of which acetyl urea, CO< lsrTT " 2 3 , and 

.7, 7 NHC2H5 1 2 

ethyl urea, C0<- NTR , are examples. 



UREIDS. 217 

Among the compounds with acids, the following may be 
mentioned : urea hydrochloride, CH 4 N 2 . HC1 ; urea nitrate, 
CH 4 N 2 O.HN0 3 ; and urea phosphate, CH 4 N 2 . H 3 P0 4 . With 
metals it forms such compounds as that with mercuric oxide, 
HgO.CH 4 N 2 0; with silver, CH 2 N 2 . Ag 2 , etc. With salts it 
forms such compounds as HgCl 2 .CH 4 N 2 0, HgO.CH 4 N 2 O.HN0 3 , 
etc. 

Substituted ureas — that is, those derivatives of urea 
which contain hydrocarbon residues in place of one or all the 
hydrogen atoms — can be made from the cyanates of substi- 
tuted ammonias. The fundamental reaction is the spontaneous 
transformation of ammonium cyanate into urea : — 

CN . ONH 4 = CO(NH 2 ) 2 . 

In the same way, cyanates of substituted ammonias are trans- 
formed into substituted ureas : — 

CN . ONH 3 C 2 H 5 = CO < ^° 2H5 ; 

JN xi 2 

CN . ONH 2 (C 2 H 5 ) 2 = CO < ^^H etc. 

-Nil 2 

The urea derivatives which contain acid radicals are made 
by treating urea with the acid chlorides : — 

CO<^ 2 + C 2 H 3 OCl = CO<™- CaH80 + HCl. 
Nil., NIL 

Acetyl uiva. 

Note for Student. — In what sense is acetyl urea analogous to 
aoetainide ? 

Ureids are compounds derived from urea by the substitution 
of acid residues for one or more of the hydrogen atoms. Thus. 

, i ,,,, Nil . OC.C1I, - , • , , ri , 

acetyl urea., ()( < ", is a simple ureid. 1 he rela- 

tion between the acid and urea in the ureid is like that between 
the acid ami ammonia in the amide: — 



218 MIXED COMPOUNDS CONTAINING NITROGEN. 

CH 3 . COOH + HH 2 N = CH 3 . CONH 2 + H 2 ; 

Acid. Amide. 

CH 8 .COOH + HHN_ rn _CH,.COHN_ m , „,. 
H 2 N >C °- H 2 N >C ° + H2 °- 

Acid. Urea. Ureid. 

The ureids of dibasic acids resemble in the same way the 
amides of these acids. One urea residue takes the place of 
the two acid hydroxyls. Thus, in the case of oxalic acid the 
relation is shown by the formulas below : — 

COOH HM co= • \ CO + 2H 2 0. 

cooH^Hmr co.hx/ 

Oxalic acid. Urea. Ureid of oxalic acid. 

There are several compounds of this kind that are of 
importance : — 



CO . HN\ 



\ 1 
>CO .— 

CO.HN X J 



This 



Parabanic acid, 

Oxalyl urea, \ C 3 H 2 N 2 3 

Oxal-ureid, 

is formed by boiling uric acid with strong nitric acid and with 
other oxidizing agents, and by treating a mixture of oxalic acid 
and urea with phosphorus oxychloride. It acts like an acid, 
the hydrogen of the imide group being replaceable by metals 
as in succinimide. Its salts readily pass over into salts of 
oxaluric acid when treated with water : — 



CO.HN x COOH 

I >CO + H 2 0= | 

CO . HN X CO . HN . CONH 2 . 



/ CO. OH 

tUcO.HN.CO.NH2A 



Oxaluric acid, CsH4N 2 OA= CO . HN . CO. NH 2 /, bears to 
parabanic acid the same relation that oxamic acid bears to 
oxamide. It occurs in the form of the ammonium salt in small 
quantity in human urine. With phosphorus oxychloride it 
gives parabanic acid. 



URIC ACID. 219 

Barbituric acid, malonyl urea, 

C4H4N2O3 + 2 H2O ( = OH2 < co ' NH > °° ) * — Barbitliric 
acid, like parabanic acid, is a product obtained from uric acid. 
It has been made artificially by treating a mixture of malonic 
acid and urea with phosphorus oxychloride : — 

c ^<cooS +co <S= CH ^co:SS> co+2H ^ 

Treated with an alkali, barbituric acid breaks up into malonic 
acid and urea. 

The relation of the acid to malonic acid and urea is the same 
as that of parabanic acid to oxalic acid and urea. 

Sulpho-urea, Thio-urea, CS(NH2)2. — This substance is 
formed by heating ammonium sulpho-cyanate, the reaction 
which takes place being analogous to that by which urea is 
formed from ammonium cyanate : — 

NCSNH 4 = SC(NH 2 ) 2 . 

It forms rhombic prisms melting at 172°. It combines with 
one equivalent of acids, forming salts. 

A number of derivatives of sulpho-urea have been made. 
They resemble those obtained from urea. 

Uric acid, CsH^N-iO;;. — Uric acid occurs in human urine 
in small quantity, in the urine of carnivorous animals, and in 
the excrement of birds and of reptiles. The excrement of 
reptiles consists almost wholly of ammonium urate. In gout, 
uric acid is deposited in the joints, under the skin, ami in the 
bladder as calculi, in the form of insoluble aeid salts. 

Uric acid forms colorless, crystalline scales, and is almost 
insoluble in water. It acts like a weak dibasic acid. 

By treating the lead salt of uric aeid with methyl iodide. 
two isomeric methyl-uric acids can he obtained, and these can 
be further converted into a tetra-inetlnl-urie aeid. which is 
derived from uric acid In the substitution o\' four methyl 



220 MIXED COMPOUNDS CONTAINING NITROGEN. 

groups for the four hydrogen atoms, C 5 (CH 3 ) 4 !N" 4 03. When 
this is decomposed, all the methyl groups are given off in 
combination with nitrogen as methyl-amine. This shows that 
uric acid contains four imine groups, as shown in the formula 
C 5 (NH) 4 3 . Other transformations show that the constitution 
of the acid must be represented by the formula 

NH - CO 
I I 

CO C - NH X 

I II >co. 

NH-C- NH/ 

According to this, uric acid contains two urea residues com- 

CO 

bined in different ways with the group c • It is to be re- 

II 

c 

garded as a diureid of a trihydroxyacrylic acid, C(OH) 2 = 
C(OH) . C0 2 H. That this view is correct has been shown by 
the artificial preparation of the acid. 

It will be seen that uric a,cid contains residues not only of 
urea, but of parabanic acid, of barbituric acid, and of a ureid 
of mesoxalic acid (alloxan). 

Xanthine, C5H4N4O2, is found in all the tissues of the 
body and in the urine, in some rare urinary calculi, and in 
several animal liquids. It is formed by the action of nitrous 
acid on guanine : — 

C 5 H 5 N 5 + HN0 2 = C 5 H 4 N 4 2 + H 2 + N* 

In this case the nitrous acid causes a substitution of an 
oxygen atom for an imine group. 

Theobromine, ) _, __ ^ _ _. r _ __ ._,__ N _. _ _ _ . 

Dimethyl-xanthine,} C7H8N4 ° 2[:z:C5H2(CH3)2N402] ' 1S a 
substance found in chocolate prepared from the seed of the 
cacao tree. It has been made by treating the lead compound 
of xanthine with methyl iodide. 



RETROSPECT. 221 

Caffeine, theine, trimethyl-xanthine, 

■ C8HioN402 + H20[=aH(CH 3 ) 3 N40 2 + H20j, is the active 
constituent of coffee and tea. It has been made from theo- 
bromine by the introduction of a third methyl group. 

Thus, as will be seen, a close connection is established 
between the active constituents of coffee, tea, and chocolate 
on the one hand, and xanthine and guanine on the other. 

Guanine, CsHsNcO^CsHsCNH^^O], is found principally 
in guano, from which it is prepared. Nitrous acid converts it 
into xanthine. Oxidizing agents convert it into guanidine, 
CN 3 H 5 (see p. 213). 

Retrospect. 

Before passing on to the next division of our subject, it will 
be well to recall briefly what we have thus far learned. 

In the first place, all the compounds which we have con- 
sidered may be regarded as derived from the marsh-gas hydro- 
carbons or paraffins. 

By replacing the hydrogen atoms of these hydrocarbons with 
chlorine, bromine, or iodine, we get (1) the substitutioi-products 
of the hydrocarbons. 

By introducing hydroxyl into a hydrocarbon in place o\ 
hydrogen, we get the bodies called (2) alcohols, of which 
there are three classes: (a) the primary, (6) thfe secondary, 
and (c) the tertiary alcohols. 

By oxidizing primary alcohols we get (3) aldehydes. 

By oxidizing secondary alcohols we get oh ketone*. 

By oxidizing alcohols, aldehydes, and ketones, wo gel (5) 
acids. 

Acids and alcohols act upon each other, forming (6) ethereal 
salts, and alcohols can be converted into (7) ethers. 

Corresponding to the oxygen derivatives, we met with com- 
pounds containing sulphur, as (8) the sulphur alcohols, or mer* 
captans; (9) the sulphur ethers; and ^\0) the sulphonic acids. 



222 MIXED COMPOUNDS CONTAINING NITROGEN. 

Next, we found compounds containing nitrogen. Under 
head we considered cyanogen, and the allied compounds h 
cyanic, cyanic, and sulpho-cyanic acids. Allied to these 
found (11) the cyanides, and (12) the isocyanides; (13) the 
cyanates, and (14) the isocyanates; (15) the sulpho-cyanates, 
and (16) the iso-sulpho-cyanates or mustard oils. 

Finally, we found (17) compounds containing metals in com- 
bination with radicals. 

Eepresentatives of these various classes of compounds were 
studied, and the relations between them pointed out. 

We found poly-acid alcohols and poly-basic acids. 

Under the head of mixed compounds were found compounds 
which belong at the same time to two or more of the funda- 
mental classes, as the hydroxy -acids, the carbo-hydrates, and the 
amino-acids. A consideration of the amino-acids and the acid 
amides brought us naturally to the consideration of urea and 
its derivatives, and of uric acid and its derivatives. 

We turn now to a new class of compounds, known as unsatu- 
rated compounds. 



CHAPTER XIII. 

UNSATURATED CARBON COMPOUNDS. - DIS- 
TINCTION BETWEEN SATURATED AND 
UNSATURATED' COMPOUNDS. 

Most of the compounds thus far studied are generally called 
saturated compounds. This is certainly an appropriate name 
so far as the hydrocarbons themselves and some of the classes 
of their derivatives are concerned. The expression " saturated " 
is intended to signify that the compounds have no power to 
unite directly with other compounds or elements. Thus marsh 
gas cannot be made to unite directly with anything. Bromine, 
for example, must first displace hydrogen before it can enter 
into combination : — 

CH 4 + Br 2 = CH 3 Br + HBr. 

The compound is saturated. 

On the other hand, a compound which can take up elements 
or other compounds directly is called unsaturated. Thus. 
phosphorus trichloride is unsaturated, for it has the power 
to take up two chlorine atoms, thus: — 

PC1 8 + C1 2 = PCI* 

Ammonia is unsaturated, for it can take up an equivalent of 
an acid : — 

Nil, -l I UM - NH4CI. 



224 UNSATURATED CARBON COMPOUNDS. 

The condition of unsaturation is met with among carbon 
compounds in several forms : — 

First. The aldehydes act like unsaturated compounds, as 
shown in their power to take up ammonia, hydrocyanic acid, 
and other substances. 

Second. The ketones also act like unsaturated compounds, 
though their power in this way is less marked than that of the 
aldehydes. 

Third. The substituted ammonias are unsaturated, in the 
same sense in which ammonia itself is unsaturated. 

Fourth. The cyanides take up hydrogen directly, and are 
therefore unsaturated also. 

In the substituted ammonias the unsaturation is due to the 
same cause as that in ammonia. In them the nitrogen is tri- 
valent. In contact with acids it becomes quinquivalent, and 
saturates itself. 

In the cyanides carbon and nitrogen are probably linked 
together in a different way from that in the substituted 
ammonias, and when hydrogen is added to the cyanogen 
group, — C = N, the condition is changed to that which is 
characteristic of the substituted ammonias : — 

H-CeeN + 2 H 2 = H 3 C-KtX, 

In the aldehydes and ketones, carbon is in combination with 
oxygen in the carbonyl condition. When they unite with 
hydrogen and some compounds, such as hydrocyanic acid, the 
relation between the carbon and oxygen is probably changed 
to the hydroxyl condition. The changes are usually repre- 
sented by formulas such as the following : — 

CH 3 .C\^ + H 2 = CH 3 .C^jj , 
(CH 3 ) 2 C = + HCN - (CH 3 ) 2 C<^. 



UNSATURATED CARBON COMPOUNDS. 225 

In carbonyl the oxygen is represented as held by two bonds 
to the carbon atom, while in hydroxy 1 it is represented as held 
by one bond. The signs may be used if not too literally inter- 
preted. There are undoubtedly two relations which carbon 
and oxygen bear to each other in carbon compounds. These 
relations may be called the hydroxyl relation, represented by 
the sign C — — , and the carbonyl relation, represented by the 
sign C = 0. 

Fifth. There is a fifth kind of unsaturation, dependent upon 
differences in the relations between carbon atoms, and it is this 
kind which is ordinarily meant when unsaturated carbon com- 
pounds are spoken of. 

The kind of relation between the carbon atoms in all the 
saturated hydrocarbons is, so far as we know, the same as that 
which exists between the two carbon atoms of ethane, and 
this is represented by the formula H 3 C — CH 3 . This formula 
signifies simply that the two carbon atoms are held together 
by the forces which in marsh gas enabled each methyl group to 
hold one hydrogen atom. Abstracting one hydrogen atom from 
marsh gas, union is effected between the carbon atoms. What 
would result' if two hydrogen atoms were to be abstracted, and 
union between the carbons then effected? Theoretically we 
should get a compound made up of two groups CH 2 , thus 
CH 2 .CH 2 , and presumably the relation between the carbon 
atoms in this compound would be different from the relation 
between the carbon atoms in ethane. Without pushing these 
speculations farther, it may be said that there is a well-known 
hydrocarbon of the formula. (\>H, which differs markedly from 
ethane. It shows the property of unsaturation very clearly 
This is olefiant gas or ethylene. It is the first of an homologous 
series of hydrocarbons, only a few of which are well known. 
These hydrocarbons yield derivatives like the paraffins J 
though of these, as well as o( the hydrocarbons, very few 
are known as compared with the number oi' the paraffin 
derivatives. 



226 UNSATURATED CARBON COMPOUNDS. 

ETHYLENE AND ITS DERIVATIVES. 
Hydrocarboxs, C n H 2n , the Olefines. 

The principal hydrocarbons of this series are included in the 
subjoined table : — 

Ethylene, Ethene C 2 H 4 . ^ H-»- 

Propylene, Propene C 3 H 6 . 

Butylene, Butene C 4 H 8 . 

Amylene, Pentene C 5 H 1( ^* 

Hexylene, Hexene CeH^. 

Heptylene, Heptene C 7 H 14 . 

The members are homologous with etlrylene. They bear to 
the paraffins a very simple relation, each one .containing two 
atoms of hydrogen less than the paraffin with the same number 
of carbon atoms. 

Ethylene, defiant gas, C 2 H 4 (= CH 2 .CH 2 ). — This gas is 
formed when many organic substances are subjected to dry 
distillation. The two principal reactions which yield it are : — 

(1) The action of an alcoholic solution of potassium hydrox- 
ide on ethyl chloride, bromide, or iodide : — 

C 2 H 5 Br + KOH = C 2 H 4 + KBr + H 2 0. 

This is the most important reaction for the preparation of the 
unsaturated compounds of the ethylene series. It is applicable 
not only to the hydrocarbons but to substances belonging to 
other classes. By means of it we have it in our power to pass 
from any saturated compound to the corresponding unsaturated 
compound of the ethylene series. Thus we pass from ethane, 
C 2 H 6 , to ethylene, C 2 H 4 , by first introducing bromine, and then 
abstracting hydrobromic acid from the mono-bromine substi- 
tution-product. By treating the mono-bromine substitution.- 



UNSATURATED CARBON COMPOUNDS. 227 

products of other saturated compounds in the same way, the 
corresponding unsaturated compounds can be made. 

(2) The action of sulphuric acid and other dehydrating agents 
upon alcohol : — 

C 2 H 5 .OH = C 2 H 4 + H 2 0. 

Experiment 51. In a flask of 2 1 to 3 1 capacity put a mixture of 
25s alcohol and 150s ordinary concentrated sulphuric acid. Heat to 
160° to 170°, and add gradually through a funnel tube about 500 cc of a 
mixture of 1 part of alcohol and 2 parts of concentrated sulphuric 
acid. Pass the gas through three wash bottles containing, in order, 
sulphuric acid, caustic soda, and sulphuric acid. Then pass it into 
bromine contained in a cylinder, provided with a cork with two holes. 
If the cylinder has a diameter of about 5 cm , let the layer of bromine 
be about 5 cm to 7 em deep. Upon it pour a somewhat deeper layer of 
water. Place the cylinder in a vessel containing cold water. Pass 
the gas into the bromine until it is completely decolorized. (See note, 
next page.) 

Ethylene is a colorless gas which can be condensed to a 
liquid. It burns with a luminous flame. With oxygen it 
forms a mixture which explodes when ignited. Its most char- 
acteristic property is its power to unite directly with other sub- 
stances, particularly ivith the halogens and with the hydrogen acids 
of the halogens. Thus it unites with chlorine and bromine, and 
with hydriodic and hydrobromic acids : — 

C 2 H 4 -f- Cl 2 = C H 4 01o ; 
C 2 H, + Br 2 = C 2 H 4 Kr 2 ; 
C 2 H 4 + HBr = (\,H 5 Br; 
C 2 H 4 + HI = (\H,l. 

The products formed with chlorine and bromine are called 
ethylene chloride and ethylene bromide. They have boon men- 
tioned under the head of halogen derivatives of the paraffins. 
They are isomeric with ethylidene chloride and ethylidene bromide. 
which are formed by substitution of chlorine or bromine for 
two hydrogens of ethane. 



228 ETHYLENE. 

Note. — The addition of bromine to ethylene is illustrated by the 
experiment last performed, in which ethylene bromide is formed. To 
purify the product, put a little dilute caustic soda in the cylinder, and 
shake. Remove the upper layer of water, and repeat the washing with 
dilute caustic soda. Then wash with water two or three times, each 
time removing the water with the aid of the pipette described on p. 31. 
Finally, put the oil in a flask, add a few pieces of granulated calcium 
chloride, and allow to stand. Pour off into a dry distilling-bulb, and 
distil, noting the temperature. 

A question which we may fairly ask concerning the structure 
of ethylene is this : Does it consist of two groups CH 2 , or of 
a methyl group, CH 3 , and CH ? Is it to be represented by the 
formula CH 2 .CH 2 or CH 3 .CH? Perhaps the clearest answer 
to this question is found in the fact that the chloride formed by 
addition of chlorine to ethylene, and that formed by replacing 
the oxygen in aldetryde by chlorine, are not identical. All 
evidence is in favor of the view that aldelryde is correctly 

represented by the formula CH 3 .C H . Hence, as has been 

pointed out, the chloride obtained from it must be represented 
thus, CH 3 .CHC1 2 . Hence, further, it appears highly probable 
that the isomeric chloride obtained from ethylene must be 
represented thus, CH 2 C1.CH 2 C1. Now, as this substance is 
formed by direct addition of chlorine to ethylene, ethylene has 

CH 2 ^-*-*-3 

the formula | , and not I 

CH 2 CH 

Nothing is known in regard to the relation between the two 

carbon atoms of ethylene, except that it is probably different 

from that which exists between the carbon atoms of ethane. 

CH 2 
It is usually represented by the sign = ; thus, 11 . We must 

CH 2 

necessarily leave the question open as to the relation between 
the carbon atoms in ethylene. If the above sign is used, it 
should serve mainly as an indication of the kind of unsaturation 
met with in etlrylene, the compound in whose formula it is 
written having the power to take up two atoms of bromine, a 
molecule of hydrobromic acid, etc. 



ALLYL ALCOHOL. 229 

The homologues of ethylene bear the same relation to it that 
the homologues of ethane bear to this hydrocarbon. Propylene 

CH.CH 3 

is methyl-ethylene, II , just as propane is methyl-ethane, 

CH 2 .CH 3 CH2 ,,..,_. CH.CH 3 C(CH 3 ) 2 

I . .Butylene is dimetnyl-ethylene, n , or n ' 

CH 3 CH.C2H5 CH.CH 3 CH 2 

or ethyl-ethylene, II . That is to say, in the hydro- 

CH 2 

carbons of the ethylene series the ethylene condition between 
carbon atoms occurs only once. 



Alcohols, C n H 2n O. 

These alcohols bear to the ethylene hydrocarbons the same 
relation that the alcohols of the methyl alcohol series bear to 
the paraffins. Only one is well known. This is the second 
member, corresponding to propylene. 

Allyl alcohol, 3 H 6 O(= CH 2 = CH.CH 2 OH). — This alco- 
hol is formed in several ways from glycerol. 

1. By introducing two chlorine atoms into glycerol in the 
place of two hydroxyls, thus getting dichlorhydrm, C 3 H 5 Clo.OH : 

CH 2 OH CHoCl 

TTP1 ' 
CHOH + „^_ = 01101 +LMLO; 

I HC1 I 

CH 2 OH CH,,01l 

and treating the dichlorhydrin with sodium, which extracts the 
chlorine : — 

OILOl CH a 

I II 

CHOI +2Na = CH +2NaCl. 

I I 

CIIoOH CH 8 OH 



230 UNSATURATED CARBON COMPOUNDS. 

2. By treating glycerol with the iodide of phosphorus. This 
gives allyl iodide, C 3 H 5 I. By treating the iodide with silver 
hydroxide it is converted into the alcohol. 

3. Most readily by treating glycerol with oxalic acid, as in 
the preparation of formic acid. The mixture is heated to 220° 
to 230°, when allyl alcohol passes over. The first product 
formed in this case is an ethereal salt of formic acid and 
glycerol, HOH 2 C.CHOH .CH 2 O.COH. At a higher temperature 
this breaks down, yielding allyl alcohol, HOH 2 C.CH = CH 2 , 
carbon dioxide and water. 

Allyl alcohol is a colorless liquid boiling at 96.5°. It has a 
disagreeable penetrating odor and is miscible with water in all 
proportions. 

Nascent hydrogen does not act upon it, or at least the action, 
if any, takes place with difficulty. As far as composition is 
concerned, the relation between allyl alcohol and propyl alcohol 
is the same as that between ethylene and ethane : — 

C 3 H 5 . OH + H 2 = C 3 H 7 . OH. 

Allyl alcohol forms esters with acids and gives the other 
reactions for alcoholic hydroxyl. It is, further, a primary 
alcohol, as it is converted by certain oxidizing agents into the 
corresponding aldehyde (acrolein) and acid (acrylic acid). 

When treated with a dilute solution of potassium permanga- 
nate it is converted into glycerol : — 

CH 2 CH 2 OH 

II I 

CH + + H 2 = CHOH. 

I I 

CH 2 OH CH 2 OH 

Allyl compounds. — Among the derivatives of allyl alcohol 
which are of special interest is allyl sulphide, (C 3 H 5 ) 2 S, which 
is the chief constituent of the oil of garlic. It can be made 
artificially by treating allyl iodide with potassium sulphide: — 

2 C 3 H 5 I + K 2 S = (C 3 H 5 ) 2 S + 2 KL 



ALLYL MUSTARD OIL. 231 

It is a colorless, oily liquid of a disagreeable odor, only slightly 
soluble in water. 

Allyl mustard oil, SCN • C3H5. — Under the head of Sulpho- 
cyanates mention was made of a series of isomeric compounds 
called isosulpho-cyanates or mustard oils. The sulpho-cyanates 
of the alcohol radicals are made from potassium sulpho- 
cyanate. Thus, methyl sulpho-cyanate is made by mixing 
together potassium methyl-sulphate and potassium sulpho- 
cyanate, and distilling: — 

NCSK + ^ 3 ° I S0 2 = K 2 S0 4 + NCSCH 3 . 

The mustard oils, on the other hand, are made by a com- 
plicated reaction from carbon disulphide and substituted 
ammonias. The conduct of the sulpho-cyanates led to the 
conclusion that they must be represented by the formula 
NC — SR, while that of the isosulpho-cyanates or mustard oils 
led to the formula SC — NR, as representing their structure. 
Allyl mustard oil is the chief representative of the class of 
bodies known as mustard oils. It occurs as a glucoside (see 
p. 185) in mustard seed. From the glucoside it is formed by 
fermentation. It also occurs in horse-radish. It is formed by 
treating allyl iodide with potassium sulpho-cyanate. If this 
reaction consisted simply in the substitution of the allyl group, 
C 3 Hr„ for potassium the product should be allyl sulpho-cyanate, 
C 3 H 5 S — ON. As a matter of fact it is the isosulpho-cyanate 
C 8 H 5 N — CS. As has already been pointed out (see p. 91), the 
sulpho-cyanates are converted into the isosulpho-cyanates by 
heat, so that the formation of the isosulpho-cyanate in tins 
case is not surprising. 

Allyl mustard oil is a liquid, boiling at 150.7°. ami having a 
very pungent odor. 

Zinc and hydrochloric acid convert it into allvl-anunc. 
NHo.O s H 5 , hydrogen sulphide and carbon dioxide. This re- 



232 UNSATURATED CARBON COMPOUNDS. 

action indicates that in allyl mustard oil the radical allyl is 
in combination with the nitrogen and not with the sulphur. 

Note for Student. — What change do the mustard oils in general 
undergo when treated with nascent hydrogen ? What change do the 
sulpho-cyanates undergo when oxidized ? 

Acrolein, acrylic aldehyde, CsH^OC^ C2H3COH). — Acro- 
lein can be made by careful oxidation of allyl alcohol. It is 
formed by the dry distillation of impure glycerol, which breaks 
up into water and acrolein : — 

C 3 H 8 3 = C 3 H 4 + 2 H 2 0. 

It is, hence, formed also by heating the ordinary fats, the 
peculiar penetrating odor noticed when fatty substances are 
heated to a sufficiently high temperature being due to the forma- 
tion of acrolein. It is prepared best by heating glycerol with 
acid potassium sulphate. 

Experiment 52. In a test-tube mix anhydrous glycerol (1 part) 
and acid potassium sulphate (2 parts), and heat the mixture. Pass the 
vapors through a bent tube into water contained in another test-tube. 
Notice the odor. Try the effect on a dilute solution of nitrate of silver. 
What is the meaning of this reaction ? 

Acrolein is a volatile liquid which boils at 52.4°. It has an 
extremely penetrating odor, and its vapor acts violently upon 
the eyes, causing the secretion of tears. 

Acrolein takes up oxygen from the air, and is converted into 
the corresponding acid, acrylic acid, C 3 H 4 2 (which see). 

It takes up hydrogen, and is thus converted into allyl alcohol. 

It takes up hydrochloric acid, and is converted into /?-chlor- 
propionic aldehyde : — 

C 2 H 3 . COH + HC1 = CH 2 C1 . CH 2 . COH. 

/3-Chlor-propionic aldehyde. 

The first two reactions are characteristic of aldehydes in 
general ; the last one is characteristic of unsaturated compounds 
belonging to the ethylene group. Acrolein, like ordinary aide- 



ACRYLIC ACID. 



233 



hyde, forms polymeric modifications which can easily be recon- 
verted into acrolein. 

It unites with ammonia, forming acrolein-ammonia, and with 
other substances in much the same way as ordinary aldehyde 
does. It unites with bromine to form acrolein dibromide, which 
when treated with barium hydroxide gives /-fructose (which see). 

Acids, C n H 2n _ 2 2 . 

Eunning parallel to the ethylene series of hydrocarbons, and 

bearing the same relation to it that the fatty acid series bears 

to the paraffins, is a series of acids of which the first member 

is acrylic acid, C 3 H 4 2 . Several members of the series are 

known. The principal members are named in the subjoined 

table : — 

ACRYLIC ACID SERIES. 





Acids 


, C n H 


2n — 


A. 




Acrylic 


acid 




C 3 H 4 2 . 


Crotonic 


u 










G 4 H 6 2 . 


Angelic 


a 










C 5 H 8 2 . 


Hydrosorbic 


a 










CeH 10 O L ,. 


Teracrylic 


a 










CzHjA. 


Cimic 


a 










CisHjsOa 


Hypoggeic 


a 










( \.;H.. Oo 


Oleic 


a 










C 18 H ,,0 


Erucic 


a 










(\,H,,0, 



Of most of the higher members of the series several isomeric 
modifications arc known. Only a few of these acids will be 
considered here. 

Acrylic acid, 8 H40a(OHa=OH.OOaH).— This acid has 
already been mentioned in connection with hydraorylic acid, 
which, when heated, breaks up into nervlie aeid and water; — 



234 UNSATURATED CARBON COMPOUNDS. 

CH 2 . OH . CH 2 . C0 2 H = CH 2 . CH . C0 2 H + H 2 0. 

Hydracrylic acid. Acrylic acid. 

Note for Student. — This reaction is analogous to that which takes 
place when ordinary alcohol is converted into ethylene. In what does the 
analogy consist ? What acid is isomeric with hydracrylic acid ? How 
does it conduct itself when heated ? Compare the transformation of 
hydracrylic acid into acrylic acid with that of malic into malei'c and 
fumaric acids, and with that of citric into aconitic acid. 

Acrylic acid can be made by careful oxidation of acrolein 
with silver oxide. The relations between propylene, C 3 H 6 , 
allyl alcohol, C 3 H 5 .OH, acrolein, C 2 H 3 .COH, and acrylic acid, 
C 2 H 3 .C0 2 H, are the same as those between any hydrocarbon of 
the paraffin series, and the corresponding primary alcohol, 
aldehyde, and acid. 

Acrylic acid can be made further by treating /2-iodo-propi- 
onic acid with alcoholic caustic potash: — 

CH 2 I.CH 2 .C0 2 H = CH 2 .CH.C0 2 H + HI. 

Note for Student. — Compare this reaction with that by which ethyl- 
ene is made from ethyl bromide. 

Acrylic acid is a liquid having a pungent odor. It boils at 
140°, and solidifies at 7°. 

Nascent hydrogen converts it into propionic acid. Hydri- 
odic acid unites directly with it, forming /3-iodo-propionic acid. 

Note for Student. — What are the analogous reactions with allyl 
alcohol and acrolein ? 

Crotonic acid, C4H6O2 Ordinary or solid crotonic acid 

is formed, (1) By hydrolyzing allyl cyanide; (2) By distilling 
/3-hydroxy-butyric acid; (3) By treating a-brom-butyric acid 
with alcoholic caustic potash; (4) By heating malonic acid 
with paraldehyde and acetic anhydride. 

Allyl cyanide must have the structure represented by the 
formula CH 2 =CH.CH 2 .dN", and we should naturally expect 
that the acid formed from it by hydrolysis would have the 



OLEIC ACID. 235 

formula CH 2 =CH.CH 2 .C0 2 H. But, on the other hand, the 
abstraction of hydrobromic acid from a-brom-butyric acid, 
CH 3 .CH 2 .CHBr. C0 2 H, should give an acid of the formula 
CH 3 .CH = CH.C0 2 H. So also the formation of crotonic acid 
from paraldehyde and malonic acid points to the formula 
CH 3 .CH = CH.C0 2 H for crotonic acid: — 

PO TT Of) TT 

(1) CH3.CHO + CH 2 < ~~*£ = CH 3 .CH = C < ~~^ + H 2 ; 

Aldehyde. Malonic acid. 

(2) CH 3 .CH = C < ZZ 2 ^ = CH 3 .CH = CH.C0 2 H + C0 2 . 

Crotonic acid. 

Again, when crotonic acid is fused with caustic potash, it gives 
only acetic acid : — 

C 4 H 6 2 + H 2 + = 2 C 2 H 4 2 ; 

and, as it has been shown that under these circumstances the 
breaking down takes place at the place where the double bond 
occurs, this reaction furnishes additional evidence in favor of 
the view that ordinary crotonic acid has the constitution repre- 
sented by the formula CH 3 .CH = CH.C0 2 H. 

From the above it seems probable that, when allyl cyanide 
is hydrolyzed, the position of the double bond is changed: 

CH 2 = CH.CH 2 .CN — ^CH 3 .CH = CH.C0 2 H. 

Isocrotonic acid appears to contain the same groups as crotonic 
acid, and is also to be represented by the formula : — 

CH 3 .CH:= OH. C0 2 H. 

As will be shown under Mai etc and Fumaric Acids (which see), 
the difference between the two forms of crotonic acid is prob- 
ably due to the arrangement of the constituents in space. 

Oleic acid, CisH.mO.: — This acid was referred to in con- 
nection with the fats, it being one of the three aeuls found 
most frequently in combination with glycerol. Olel'n, or 



236 UNSATURATED CARBON COMPOUNDS. 

glyceryl tri-oleate, is the liquid fat, and is the chief constituent 
of the fatty oils, such as olive oil, whale oil, etc., and of the 
fats of cold-blooded animals. It is contained also in almost all 
ordinary fats. In the preparation of stearic acid for the manu- 
facture of candles, the oleic acid is pressed out of the mixture 
of fatty acids. To prepare the acid, olein is saponified, and the 
soap then decomposed with hydrochloric acid. 

Note for Student. — Give the equations representing the reactions 
involved in passing from olem, or glyceryl tri-oleate, to oleic acid. 

Oleic acid is a crystallized substance that melts at 14°. It 
unites with bromine, forming dibrom stearic acid. Hydriodic 
acid converts it into stearic acid : — 

^i8H 34 2 + H 2 = C 18 H 36 2 . 

Oleic acid. Stearic acid. 

Polybasic Acids of the Ethylene Group. 

There are a few dibasic acids that bear to the ethylene 
hydrocarbons the same relations that the members of the oxalic 
acid series bear to the paraffins. They may be regarded as 
derived from the hydrocarbons by the introduction of two 
carboxyl groups. 

Acids, C2H2(C02H)2- — There are two acids of this formula, 
fumaric and maleic acids, both of which are formed by the dis- 
tillation of malic acid. 

Fumaric acid can also be made by treating brom-succinic 
acid with alcoholic potash. 

Both fumaric and maleic acids are converted into succinic 
acid by nascent hydrogen, and into brom-succinic acid by 
hydrobromic acid : — 

Malic acid. Maleic or Fumaric acid. 

cABr< co;2 = cA <co:S +HBr; 

Brom-succinic acid. Fumaric acid. 



POLYBASIC ACIDS OF THE ETHYLENE GIIOTJP. 237 



COoH 



C0 9 H 



Maleic or Fumaric acid. Succiuic acid. 



An extension of the fundamental ideas of stereochemistry 
furnishes an explanation of the relation between maleic and 
fumaric acids. According to these ideas, a carbon atom in 
combination with four atoms or groups of atoms holds these 
atoms or groups by bonds directed toward the solid 
angles of a tetrahedron, the carbon atom itself 
being at the centre of the tetrahedron. When two 
carbon atoms unite in the simplest way, the stereo- 
chemical model representing the compound con- 
sists of two tetrahedrons united at one of the solid 
angles of each, thus : — 

When two carbon atoms unite by a double bond, 
as in the ethylene compounds, the model consists 
of two tetrahedrons united by one of the edges of 
each, thus : — 

In case each carbon is in combination with two unlike atoms 
or groups, there are two ways in which these can be arranged in 
space, as shown by the figures : — 






It will be seen that, in the first of these figures, A and C are 
on one side, and B and 1> on the other side: while in the sec- 



238 UNSATURATED CARBON COMPOUNDS. 

ond figure A and D are on one side and B and C on the other. 
The two arrangements are different. In maleic and fumaric 
acids each carbon atom is in combination with one hydrogen 
atom and one carboxyl group, as shown by the ordinary 

CH . C0 2 H 
formula [| • These can be arranged in two ways cor- 

CH.C0 2 H 
responding to the above figures, thus : — 



COOH H^r ^COOH 





COOH HOOC 



It is believed that figure I. represents the configuration of 
maleic acid, and figure II. that of fumaric acid. The main 
reason for this is the fact that when maleic acid is heated it 
loses water and forms an anhydride, while fumaric acid does 
not form an anhydride. As the anhydride is formed by the 
interaction of the two carboxyl groups, a substance of config- 
uration I. could form an anhydride more easily than one of 
configuration II. 

The configurations of maleic and fumaric acids can be rep- 
resented by formulas, thus : — 

H - C - COoH H - C - C0 2 H 

II II 

H - C - C0 2 H C0 2 H - C - H 

Malei'c acid. Fumaric acid. 

Maleic anhydride similarly can be represented thus : — 
H-C-CO. 



H - C - CO 



> 



POLYBASIC ACIDS OF THE ETHYLENE GROUP. 239 

This extension of the theory of stereochemistry applies to a 
large number of phenomena and furnishes a satisfactory ex- 
planation of a number of cases of isomerism for which no other 
explanation has been found. 

The two crotonic acids already referred to are believed to 
be related to each other in the same way as maleic and 
fumaric acids, as shown by the formulas : — 

CH3 — C — H CH 3 — C — H 

II II 

C0 2 H -C-H H-C- C0 2 H 

Acids, C5H6O4. — When citric acid is rapidly heated, a dis- 
tillate consisting of the anhydrides of two acids of the formula 
C 5 H 6 4 is obtained. These acids are itaconic and citraconic 
acids. When itaconic anhydride is distilled under ordinary 
pressure, it is converted into citraconic anhydride. When 
citraconic anhydride is heated for some time with water at 
150°, itaconic acid is formed. When a water solution of citra- 
conic anhydride is treated with hydrochloric or nitric acid and 
then evaporated, a third acid, mesaconic acid, isomeric with 
citraconic and itaconic acid, is obtained. 

It has been shown that citraconic and mesaconic acids are 
respectively homologues of maleic and fumaric acids, as repre- 
sented by the formulas : — 

CH 3 - C - COoH OH, - - COoH 

II II 

H - - COoH C0 2 H -C-H 

Citraconic acid. Mesaconic acid. 

Like fumaric acid, mesaconic acid does not form an anhy- 
dride. Itaconic acid is not a methyl derivative o\' maleic or 
fumaric acid, but corresponds to the formula CH a =C — CO 11 

I 

CH 2 .COjH 
The formation of itaconic and citraconic anhydrides from 
citric acid is shown thus : — 



240 UNSATURATED CARBON COMPOUNDS. 

CH 2 . C0 2 H CH . C0 2 H CH . COOH 

I AH ll 'I 

C<nL _. C.C0 2 H _^ C.CO v 

i C ° 2H ~ *" i — ^ i No 

CH 2 . C0 2 H CH 2 . C0 2 H CH 2 . CCK 

Citric acid. Aconitic acid. Aconitic anhydride. 

CH 2 CH 3 

II I 

. C . CO v C . CO v 

I >0 — >■ || >0 

CH 2 .CO/ CH.CO^ 

Itaconic acid. Citraconic anhydride. 

Aconitic acid, [CeHeOe^ CsHsCCC^H^)]. — Aconitic acid 
is the only tri-basic acid of this group that need be mentioned. 
As has been stated, it is formed when citric acid is heated to 
175°. It is found in nature in aconite root, and in the sap of 
sugar-cane and of the beet. 

Nascent hydrogen converts it into tri-carballylic acid, 
C 3 H 5 (C0 2 H) 3 . The relation between citric and aconitic acid is 
shown above. 

Acetylene and its Derivatives. 

The principal reactions by means of which it is possible to 
pass from a hydrocarbon of the paraffin series to the corre- 
sponding hydrocarbon of the ethylene series consist in intro- 
ducing a halogen into the paraffin, and then treating the 
mono-halogen substitution-product with alcoholic caustic 
potash : — 

C 2 H 5 Br = C 2 H 4 + HBr. 

The effect of these two reactions is the abstraction of two 
hydrogen atoms from the paraffin. The following questions 
therefore suggest themselves : — 

Suppose a dibrom substitution-product of a paraffin be heated 
with alcoholic caustic potash ; will the effect be that represented 
by the equation 

C 2 H 4 Br 2 = C 2 H 2 + 2 HBr ? 



ACETYLENE. 241 

And, further, suppose a mono substitution-product of an 
ethylene hydrocarbon be treated with alcoholic potash; will 
the effect be that represented by the equation 

C 2 H 3 Br = C 2 H 2 + HBr ? 

If so, it is plain that we have it in our power to make a new 
series of hydrocarbons, the members of which must bear to the 
ethylene hydrocarbons the same relation that the latter bear 
to the paraffins. The general formula of this series would be 
C n H 2n _ 2 , that of the ethylene series being C n H 2n , and that of 
the paraffin series, C n H 2n+2 . 

A few members of the hydrocarbon series, C n H 2n _ 2 , are 
known, though only one is well known, and this one alone 
need be considered. 

Acetylene (Ethine), C2H2. — Acetylene is contained in 
coal gas in small quantity. It is formed by direct combination 
of hydrogen and carbon when a current of hydrogen is passed 
between carbon poles which are incandescent in consequence 
of the passage of an electric current ; when alcohol, ether, 
methane, and other organic substances are passed through a 
tube heated to redness ; when coal gas and some other sub- 
stances are burned in an insufficient supply of air, as when 
a Bunsen burner " strikes back " ; and when ethylene bromide 
is treated with alcoholic caustic potash : — 

C 2 H 4 Br 2 = CoH 2 + 2 HBr. 

It is formed further when bromoform, CHBrg, or iodoform. 
CHI3, is treated with silver or zinc dust. 

It is easily made by the action oi % water on calcium 
carbide : — 

C a Ca + 2 11,0 = (\,H, + Ca(01IV 

This process is extensively used on the large scale for the 
preparation of acetylene for illuminating purposes. 

Experiment 53. — in a WbuUf's flask or an ordinary Florence flask 

provided with a dropping funnel and an outlet tube, put a tew pieces oi 



242 



ACETYLENE. 



calcium carbide about the size of half-inch cubes. When the water from 
the funnel is allowed to drop on the carbide the gas is given off at once, 
and the rapidity of the current can be regulated by regulating the drop- 
ping of the water. After the operation has been in progress long enough 
to drive the air out of the apparatus, connect a burner with the delivery 
tube at A, and set fire to the gas. Unless the burner is an "acetylene 
burner " the flame gives a great deal of soot and it should not be allowed 
to burn long. In the test-tube B is a strong solution of ammoniacal 
cuprous chloride prepared as follows : Make a saturated solution of 1 part 
common salt and 2| parts crystallized copper sulphate. Saturate with 
sulphur dioxide. Filter, and wash with acetic acid. Dissolve the white 




cuprous chloride in ammonia. Pass some of the gas through this solu- 
tion. The acetylene will be absorbed by the copper solution, and a pre- 
cipitate formed (see Exp. 54). 

Acetylene is a colorless gas of an unpleasant odor, resembling 
that of the leek. It burns with a luminous, sooty flame. 

When heated to a sufficiently high temperature, it is con- 
verted into the polymeric substances, benzene, C 6 H 6 , and sty- 
rene, C 8 H 8 . It unites with hydrogen to form ethylene and 



ACETYLENE. 243 

ethane. It unites with nitrogen, under the influence of the 
sparks from an induction coil, forming hydrocyanic acid : — 

C 2 H 2 + 2 N = 2 HCK 
Acetylene forms some curious compounds with metals and 
metallic oxides. Among them may be mentioned the copper 
compound obtained in Exp. 53. This has the composition 
C 2 Cu 2 , which is the cuprous salt of acetylene. It is a reddish- 
brown substance, insoluble in water. When dry, it explodes 
violently at 120°. Hydrochloric acid decomposes it, acetylene 
being evolved. 

Experiment 54. Filter off the precipitate obtained in Exp. 53, 
and wash it until the wash-water runs through colorless. Bring the 
precipitate, together with a little water, into a flask furnished with a 
funnel-tube and a delivery-tube. Slowly add concentrated hydrochloric 
acid, and notice the evolution of gas. Collect some of it in a small 
cylinder over water, and burn it. 

Acetylene acts like a weak dibasic acid. Cuprous carbide, 
C 2 Cu 2 , calcium carbide, C 2 Ca, silver carbide, C 2 Ag 2 , etc., are 
salts of the acid. 

Acetylene unites with bromine, forming the compound 
C 2 H 2 Br 4 , tetra-brom-ethane. It unites with hydrobromic and 
hydriodic acids, forming substitution-products of the saturated 
hydrocarbons : — 

C 2 H 2 + 2 HI = C S H 4 L. 

The union between the carbon atoms in acetylene is com- 
monly represented by three lines (=), or three dots ( : ). 

CH 
Thus acetylene is written III or CH : CH. Like the siam o\' 

CH 
the ethylene condition the sign o( the acetylene condition 
should not be interpreted too Literally. • It is best to regard it 
as the sign of the condition illustrated by acetylene. This 
condition carries with if the power to take up join- atoms of a 
halogen, or hvo molecules of hydrobromic acid and similar acids, 
and to form metallic dericatices like (hose of ac above 

referred to, 



244 UNSATURATED CARBON COMPOUNDS. 

Most of the higher members of the acetylene series of hydro- 
carbons bear to acetylene the same relation that the higher mem- 
bers of the ethylene series bear to ethylene. The first one is 

C.CH 3 
Allylene or methyl-acetylene . . . . ||| ; 



the second is 

Ethyl-acetylene 



or Dimethyl-acetylene 



CH 

C . C 2 H 5 

HI 
CH 

C.CH 3 



C.CH 3 



It should be noticed in this connection that there is a hydro- 
carbon of the formula C 4 H 6 , which, strictly speaking, is not 
a homologue of acetylene, though it is very closely allied to 

CH = CH 2 
dimethyl-acetylene. It has the formula I 

CH = CH 2 

The homologues of acetylene may be divided into two classes : 

1. Those which are obtained from acetylene by the replace- 
ment of one or both the hydrogen atoms by saturated radicals, 
such as methyl, ethyl, etc. These are called the true homologues. 
They all retain the condition peculiar to acetylene. 

2. Those in which the ethylene condition occurs twice, as in 
the hydrocarbons of the formulas 

CH = CH 2 C(CH 3 ) 2 

I , || etc. 

CH = CH 2 C = CH 2 

These may be called diethylene derivatives. These, like acety- 
lene and its true homologues, have the power to take up four 
atoms of a halogen, or two molecules of hydrobromic acid and 
similar acids, but they do not form copper and silver salts. 

Propargyl alcohol, C3H4O. — This alcohol is mentioned 
merely as an example of alcohols which are derived from the 
acetylene hydrocarbons. It is the hydroxyl derivative of 



SORBIC ACID. 245 

allylene, or methyl-acetylene. It is made by treating brom- 
allyl alcohol, C 3 H 4 Br. OH, with alcoholic caustic potash: — 

CH 2 OH CH 2 OH 

| = | +HBr. 

CBr = CH 2 C = CH 

Acids, C n H 2n _ 4 2 - 

These acids are the carboxyl derivatives of the acetylene 
hydrocarbons, and hence differ from the members of the 
acrylic acid series by two atoms of hydrogen each, and from 
the members of the fatty acid series by four atoms of hydro- 
gen each. 

/OH x 

Propiolic acid, C3H2O2 III • — The potassium salt of 

this acid has been made from the acid potassium salt of acety- 

C . C0 2 H 
lene-dicarbonic acid, ||| , by heating it in water solution. 

C . C0 2 H 
Acetylene-dicarbonic acid is formed by heating dibrom-succinic 
acid with a water solution of caustic potash : — 

CHBr.CO,H C.COoH 
I - III +2 HBr. 

CHBr.C0 2 H C.COoH 

/C.CHa n 
Tetrolic acid, CH-iCM III ), is obtained by treating 

VC.CO2B/ 

/8-chlor-crotonic acid with caustic potash : — 

CC1.CH, C.CH a 

II - III + HC1. 

CH.CO a H (\C0,1I 

Sorbic acid, CeHsCfcCCHa . CH CH . CH - CH . OOsH). — 
This acid occurs in the unripe berries of the mountain ash. 
It takes up hydrogen and yields hydrosorbxc acid, a member of 

the acrylic acid series (see table, p. 233). It also takes up 



246 UNSATURATED CARBON COMPOUNDS. 

bromine, the final product of the action being an acid of the 
formula C 5 H 7 Br 4 . C0 2 H. With hydrobromic acid it forms 
dibrom-caproic acid : — 

C 5 H 7 . C0 2 H + 2 HBr = C 5 H 9 Br 2 . C0 2 H. 

Dibrom-caproic acid. 

It will be observed that sorbic acid is a diethylene derivative 
and that it does not contain the acetylene condition. 

Linoleic acid, CisHssCMCnHsiCC^H). — This acid occurs 
in the form of an ethereal salt of glycerol in drying oils. It can 
be obtained from linseed oil by saponification. It is an oily 
liquid, one of the most marked properties of which is its power 
to take up oxygen from the air, and turn into a solid substance. 
Linseed oil itself has this property of hardening or drying. It 
is the principal substance belonging to the class of drying oils. 
The oil is used extensively as a constituent of varnishes and 
of oil paints. 

The relations between linoleic, oleic, and stearic acids as far 
as their composition is concerned are shown by the following 
formulas : — 

Ci8H 36 2 C 18 H340 2 C 18 H 32 2 

Stearic acid. Oleic acid. Linoleic acid. 



Valylene, CsHe. — We have thus far had to deal with three 
series of hydrocarbons of the general formulas C n H 2n+2 ,C n H 2n , 
and C n II 2n _ 2 . We naturally inquire whether there is a series of 
the general formula C n H 2n _^. A few members of the series have 
been prepared by abstracting hydrogen from certain of the 
acetylene hydrocarbons by the action of alcoholic potash on the 
bromine derivatives. Thus, valylene, C 5 H 6 , has been made by 
treating valerylene bromide, C 5 H 8 Br 2 , with alcoholic potash: — 

C 5 H 8 Br 2 = C 5 H 6 + 2HBr. 

It is a liquid. Its most characteristic property is its power 
to unite with bromine to form the saturated compound C 5 H 6 Br 6 . 



DIPROPARGYL. 247 

Dipropargyl, CeHe. — Dipropargyl is obtained from the 
compound dibrom-diallyl, C 6 H 8 Br 2 , by boiling with alcoholic 
caustic potash : — 

C 6 H 8 Br 2 = C 6 H 6 + 2 HBr. 

It unites very readily with bromine, forming, as the final 
product of the action, the compound C 6 H 6 Br 8 , which is an 
octo-bromine substitution-product of hexane, C 6 H 14 . 



The unsaturated hydrocarbons and their derivatives thus far 
considered are obtained by simple reactions from the saturated 
compounds, and they all have the power to take up bromine, 
hydrobromic acid, etc., readily, and thus to pass back to the 
saturated condition. Whatever the real nature of the relation 
between the carbon atoms in all these unsaturated hydrocarbons 
may be, it certainly is easily changed to the condition that 
exists in the saturated compounds. There are several hydro- 
carbons, however, which are unsaturated but which are not 
easily converted into derivatives of the saturated hydrocar- 
bons. Although under some circumstances they with diffi- 
culty unite directly with the halogens, they do not take up 
enough to convert them into derivatives of the paraffins ; and 
the products formed are unstable, easily giving up the halogen 
atoms with which they united. The simplest hydrocarbon of 
this new kind is the well-known benzene, which is isomeric 
with dipropargyl. Before proceeding to the study of benzene 
and its derivatives, it will be well to inquire whether the 
abstraction of hydrogen by the reaction chiefly used can be 
pushed farther than it has bhus far been pushed. Can we, 
in other words, by means of this reaction get hydrocarbons 
of the formula CJ\. 2u 8 which have the power bo unite directly 
with ten atoms of bromine? Such hydrocarbons have not 
been prepared. Hydrocarbons o\' the formula C n H to 8 are 
known; but they are not made from the paraffins bv abstract- 
ing hydrogen, and they are not converted into substitution- 



248 UNSATURATED CARBON COMPOUNDS. 

products of the paraffins by the addition of halogens and halo- 
gen acids. 

The compounds which have been treated of fall under five 
general heads, according to the formulas of the hydrocarbons. 
These heads are, — 

1. Hydrocarbons, C n H 2n+2 , the paraffins and their derivatives. 

2. Hydrocarbons, C n H 2n , or olefins and their derivatives. 

3. Hydrocarbons, C n H 2n _ 2 , or the acetylene hydrocarbons and 

their derivatives. 

4. Hydrocarbons, C n H 2n _ 4 , and their derivatives. 

5. Hydrocarbons, C n H 2n _ 6 , and their derivatives. 

This classification, while strictly correct, is misleading, inas- 
much as it conveys no idea in regard to the relative importance 
of the compounds of the different classes. As we have seen, 
the only compounds whose treatment required much time are 
those of the first class. These compounds stand out promi- 
nently, and are distinguished by the frequency of their occur- 
rence and their great number. The compounds of the second 
class are much less numerous, and but a small number of them 
are familiar substances. While a few substances belonging to 
the third class are known, our knowledge in regard to the 
class is much more limited than even that of the second class. 
Finally, as regards the fourth and fifth classes, the few repre- 
sentatives of them that are known are at present scientific 
curiosities. Thus, after we leave the paraffin derivatives, our 
knowledge dwindles away very rapidly when we pass to the 
following classes, until it ends with a single compound in the 
fifth class. 

Let us now pass to the consideration of a new group, the 
importance and number of whose members entitle it to be 
placed side by side with the group of paraffin derivatives. 



CHAPTER XIV. 

THE BENZENE SERIES OF HYDROCARBONS. - 
AROMATIC COMPOUNDS. 

The fundamental substance of this group is benzene, C 6 H 6 , 
which bears to the group the same relation that marsh gas 
bears to the group of paraffin derivatives. Benzene, together 
with some of its homologues, is a product of the distillation of 
bituminous coal, and is, therefore, contained in coal tar. As 
coal tar is the raw material from which all benzene derivatives 
are obtained, it will be well briefly to consider the conditions 
of its formation and the method of obtaining pure hydrocarbons 
from it. 

Coal tar is a thick, black, tarry liquid, which is obtained in 
the manufacture of illuminating gas from bituminous coal. 
The coal is heated in retorts, and all the products passed 
through a series of tubes called condensers. These are kept 
cool, and in them the liquid and volatile solid products are con- 
densed, forming together the coal tar. It is an extremely com- 
plex mixture, from which a great many substances have been 
obtained. Among those most readily obtained from it are the 
hydrocarbons of the benzene series, as well as the hydrocarbons 
naphthalene and anthracene, both of which are important sub- 
stances. 

When the tar is heated, of course the most volatile liquids 
pass over first. These are collected in vessels containing water. 
The first portions of the distillate float on water, and constitute 
what is called the light oil. After a time hydrocarbons and 
Other substances of greater specific gravity than the light oil 

249 



250 BENZENE SERIES OF HYDROCARBONS. 

pass over. These portions sink under water, and constitute 
the heavy oil. 

The light oil is treated with caustic soda, which removes 
phenol (carbolic acid) and similar substances, and with sul- 
phuric acid, which removes certain basic compounds and olefins. 
The residue is then subjected to fractional distillation, by 
which means the first two members of the series can be ob- 
tained in very nearly pure condition. As these hydrocarbons 
form the basis of a number of important industries, they are 
separated from coal tar on the large scale. 

The principal members of the series are named in the table 
below. 

HYDROCARBONS, C n H 2n _ 6 . 

Bexzexe Series. 

Benzene C 6 H 6 . 

Toluene C 7 H 8 . 

Xylene C 8 H 10 , 

Mesitylene 

Pseudocumene 

Durene 1 

Cymene J 

Hexa-methyl benzene C^H^. 

Benzene, CeHc. — Benzene is prepared, as above described, 
from the light oil obtained from coal tar. A large part of the 
benzene now used is obtained from the gas formed in the coke 
furnaces. It is also prepared by heating benzoic acid with lime, 
when the acid breaks up into carbon dioxide and benzene : — 

C 7 H 6 2 = C 6 H 6 + C0 2 . 

Note for Student. — What is the analogous method for the prepara- 
tion of marsh gas ? 

Benzene has been made further by simply heating acetylene: — 

3 C 2 H 2 = C 6 H 6 . 



CgH^. 



BENZENE SERIES. 251 

To purify the hydrocarbon obtained by fractional distillation 
from light oil, it is cooled down to a low temperature, and that 
which does not solidify is poured off. The crystals are pressed 
in the cold between layers of bibulous paper, and are then very 
nearly pure benzene. This can be further purified by treat- 
ment with sulphuric acid, which removes a small quantity of a 
substance containing sulphur, and known as thiophene, C 4 H 4 S. 
Perfectly pure benzene is obtained by distilling pure benzoic 
acid with lime. 

Experiment 55. Mix intimately 50s benzoic acid and 100s quick- 
lime, and distil from a flask connected with a condenser. See that the 
materials and apparatus are dry. Add a little calcium chloride to the 
distillate ; and, after it has stood for an hour or two, redistil it from a 
distilling-bulb of proper size, noting the temperature at which it boils. 
Put the redistilled hydrocarbon in a test-tube, and surround it with a 
freezing mixture. 

Experiment 56. In most places where there are gas-works it will 
not be difficult to get a quantity of light oil. The separation of some 
of this into benzene and toluene, and the purification of the two hydro- 
carbons, is the best possible introduction to a study of the aromatic 
compounds. The benzene and toluene thus obtained may be used in the 
preparation of a number of typical derivatives according to methods 
which will be described. In fractioning the light oil, it will be observed 
that there is a tendency to an accumulation of the distillates in the parts 
boiling near 80.5° (the boiling-point of benzene) and 110° (the boiling- 
point of toluene). The final purification of the benzene should be effected 
by freezing and pressing, as described above. The toluene should be dis- 
tilled until its boiling-point is not changed by redistillation. 

Benzene is a colorless liquid boiling at 80.5°. It has a 
peculiar, pleasant odor. Several of (lie homologues of benzene 
have a, similar odor. Hence the name aromatic compounds was 
given to them originally, and it is still in general use. Ben- 
zene is lighter than water, its specific gravity being 0.899 at 0°. 
It is insoluble in water, soluble in alcohol and chloroform. It 
burns with a. bright, luminous, smoky flame. 

Experiment 57. Pour a layer o\' benzene on water in a small 
evaporating-dish. Set tire to it. 



252 BENZENE SERIES OF HYDROCARBONS. 

Benzene crystallizes in rhombic prisms when cooled to 0°. 
These melt at 5.4°. It is an excellent solvent for oily and 
resinous substances. 1 

Chemical conduct of benzene, and hypothesis regarding its 
structure. In the light of the knowledge we have already 
gained in studying hydrocarbons which contain a smaller pro- 
portion of hydrogen than the paraffins do, we should naturally 
expect to find that benzene can easily be converted into a 
derivative of hexane. We should naturally expect to find 
that it unites with bromine, just as dipropargyl does, to 
form an octo-brom-hexane thus, — 

C 6 H 6 +Br 8 = C 6 H 6 Br 8 ; 

with hydrobromic acid to form tetra-brom-hexane thus, ■ — 

C 6 H 6 + 4HBr = C 6 H 10 Br 4 ; 

and probably with hydrogen to form hexane, — 

C 6 H 6 + 8 H = C 6 H 14 . 

But none of these reactions takes place. Hydrobromic acid, 
which combines so readily with all the unsaturated compounds 
hitherto considered, does not act at all upon benzene. Bromine 
acts readily enough, but the action which usually takes place 
is like that which takes place with the saturated paraffins. It 
is substitution, and not addition. Thus, bromine forms mono- 
brom-benzene, C 6 H 5 Br, under ordinary circumstances. If, 
however, the action takes place in the direct sunlight, a 
product is formed which has the formula C 6 H 6 Br 6 , known as 
benzene hexabromide, and to this no more bromine can be 
added. 

Treated with hydriodic acid, benzene takes up six atoms of 
hydrogen and yields a hydrocarbon of the composition C 6 H ]2 . 
This is not a member of the ethylene series. 

1 Benzene, the chemical individual of the definite formula C 6 H 6 , must not be con- 
founded with "benzine," the commercial substance obtained in the refining of petro- 
leum (see p. 110). 



BENZENE SERIES. 253 

The facts mentioned show clearly that benzene differs in 
some way fundamentally from all the hydrocarbons which 
have been treated of thus far. But these facts are not sufficient 
to enable us to form an hypothesis in regard to its structure. 
On studying the many substitution-products of benzene, how- 
ever, we soon become acquainted with facts of a different order 
and of the highest importance. 

It will be remembered that the theory in regard to the rela- 
tions of the paraffins to each other is based upon the fact, that 
only one mono-substitution product of marsh gas can be ob- 
tained with any given substituting agent. There is but one 
chlor-methane, but one brom-methane, etc. This fact leads to 
the belief that each hydrogen atom of marsh gas bears the 
same relation to the carbon atom, or that marsh gas is a sym- 
metrical compound. A similar conclusion has been reached in 
regard to benzene; and it is based upon a most exhaustive 
study of the substitution-products. Notwithstanding almost 
innumerable efforts to prepare isomeric mono-substitution 
products of benzene, no such isomeric substances have been 
prepared. There is but one mono-brom-benzene, but one mono- 
chlor-benzene, etc., etc. Further, mono-brom-benzene lias been 
prepared by substituting bromine for each of the six hydrogen 
atoms of benzene successively ; and the product has been found 
to be the same, no matter which hydrogen is replaced. As this 
fact is of fundamental importance, it will be well to point out 
how it is possible to replace the six hydrogens successively, and 
to know that in each ease a different hydrogen atom is replaced. 
While it would lead too far to follow this subject in detail, the 
principle made use oi' can be made clear in a few words: — 

We have a compound, the formula oi' which is C„ll i; . Write 

l a 3 i 5 6 

it thus, t; l II III HUM, numbering the hydrogen symbols to facil- 

itate reference to them. The problem is to replace, say 11. b\ 

bromine; in a second case, to replace 11 In bromine; in a 

s 
third, H, etc. ; and to compare the six mono-brom-hen.vnes thus 



254 BENZENE SERIES OF HYDROCARBONS. 

obtained. Suppose we treat benzene with bromine. We get 
a mono-brom-benzene, and we know that one of the hydrogen 
atoms is replaced by bromine, but of course we cannot tell 
which one. We may assume that it is any one of the six 
represented in the above formula. For the sake of the argu- 

1 2 3 4 5 6 

ment, call it H. Our compound is therefore C 6 BrHHHHH. 
Now treat this compound with something else which has the 
power to replace the hydrogen, say nitric acid. A second 
hydrogen atom is replaced by the nitro group N0 2 . Again, 
we do not know which one of the hydrogen atoms is replaced 
in this operation, but we do know that it is a different one 
from that which tvas replaced by the bromine in the first 

2 

operation. Call it H. We have, therefore, the compound 

3 4 5 6 

C 6 Br(N0 2 )HHHH. By treating this compound with nascent 

hydrogen, two reactions take place, the chief one for our 

present purpose being the replacement of the bromine by 

i 
hydrogen. In other words, H is put back into the com- 

1 3 4 5 6 

pound again, and we have C 6 H(ISFH 2 )HHHH. By means 
of two reactions which will be studied farther on it is a 
simple matter to replace the amino group by bromine. This 

1 3 4 5 6 

done, we have the compound C 6 HBrHHHH, or a mono-brom- 
benzene, in which the bromine certainly replaces a different 
hydrogen atom from that replaced by direct substitution. The 
two products are, however, identical. The above explanation 
will serve to make clear the principle that is involved in the 
study of the relations which the hydrogen atoms contained in 
benzene bear to the molecule. The principle has been applied 
successively to all the hydrogen atoms, and, as already stated, 
the result is the proof that all these hydrogen atoms bear the 
same relation to the molecule. The same is true of the carbon 
atoms, as the compound is symmetrical. 

How can we imagine six carbon atoms and six hydrogen 
atoms arranged so that all these shall bear the same relation 



BENZENE. 255 

to the molecule ? The simplest conception is that each carbon 
is in combination with one hydrogen, and that the six carbon 
atoms are arranged in the form of a ring, and not, as in the 
paraffins, in the form of an open chain, or a chain with branches. 
Using our ordinary method of representation, this concep- 
tion is symbolized in the formula 

H 

C 




or, as the curved lines have no special significance, the expres- 
sion becomes 

H 

HC/ \CH 

I I 

H 

This symbol, then, is the expression of a thought suggested by 
a study of the chemical conduct of benzene. Before we can 
accept it as probable, it must first be tested by all the farts 
known to us. If it is not in accordance with all o( them, if 
it suggests possibilities which arc not realized, then it must 
be discarded. 

In the first place, then, does it account for the addition 
products, benzene hexabromide, hexa-hydro-benzene, etc.? The 
formula represents each carbon atom as trivalent, ami we should 
expect, therefore, that each one could take up an additional 
univalent atom, forming, in the case oi' bromine, a compound 
of the formula 



256 BENZENE SERIES OF HYDROCARBONS. 

HBr 

BrHc/ ^CHBr 

I I 

BrHC v .CHBr 

xx 

HBr 

in which each carbon atom is acting as a quadrivalent atom. 
Unless the ring form of combination between the carbon atoms 
is broken up, it is impossible for the compound to take up 
more bromine. Hence, the last product of the addition of 
bromine to benzene should be benzene hexabromide. The 
facts and the hypothesis are in harmony. 

Again, we may inquire : Of how many isomeric di-substitu- 
tion products of benzene does the hypothesis suggest the exist- 
ence ? Numbering the hydrogens in the formula, we have : — 

(1)H 

(6)HC/ \CH(2) 

I I 

(5)HCv yCH(3) 

H(4) 

The hydrogens (1) and (2), (2) and (3), (3) and (4), (4) and 
(5), (5) and (6), and (6) and (1), bear the same relations to 
each other ; and, according to the formula, whether we replace 
(1) and (2), or (2) and (3), or (3) and (4), or any other of the 
above-named pairs, the product ought to be the same. We 
should get a compound of which the following is the general 
expression, in which X represents any substituting atom or 
group : — x 

HC/ ^CX 

I I 

HCv XH 

MX 

H 

Formula I. 



BENZENE. 257 

In the second place, the hydrogens (1) and (3), (2) and (4), 
(3) and (5), (4) and (6), (5) and (1), and (6) and (2) bear to 
each other the same relation, but a different relation from 
that which the above pairs do. Replacing any such pair, we 
should have a second compound, which is represented by the 
general formula y 

I I 



H 

Formula II. 

Finally, there is a third kind of relation, which is that 
between hydrogens (1) and (4), (2) and (5), and (3) and (6) ; 
and, by replacing such a pair, we should get a compound 
represented by the general formula 

X 

HC/ ^CH 

I I 

HC V .OH 

V 

X 

Formula III. 

The hypothesis suggests no other possibilities. We see thus 
that the hypothesis indicates the existence of three, and only 
three, classes of di-substitutiou products of benzene. There 
ought to be three, and only three, di-chlor-benzenes j three, 
and only three, di-brom-benzenes, etc. 

The di-substitution products have boon studied very ex 
haustively for the purpose of determining definitely whether 
the conclusion above reached is in accordance with the tacts; 
and it may be said at once, that every tact thus far discovered 
is in harmony with the hypothesis. Three well-marked classes 
of isomeric di-substitutiou products of benzene are known, and 
only three; and many representatives of the three classes have 



258 



BENZENE SERIES OF HYDROCARBONS. 



been studied carefully. There are many other facts of less 
importance known which furnish arguments in favor of the 
benzene hypothesis expressed in the formula above discussed, 
but this is not the place to discuss them. Let it suffice, for 
the present, to recognize that the hypothesis is in accordance 
with the most important facts known to us. 

There is one point that has not been touched upon, and that 
is the relation of the carbon atoms to each other. The formula 
is commonly written thus : — 

H 

/ C v 

H(T X CH 

I II 

HC V /CH 

H 

which indicates that the carbon atoms are joined together alter- 
nately by single and by double bonds. This formula, however, 
expresses something about which we know little, and concern- 
ing which it is difficult, at present, to form any conception. 
Another formula that has been suggested is this : — 



Still another is : — 




In each of these, as will be seen, an attempt is made to account 



TOLUENE. 259 

for the fourth bond of each carbon atom. The question in- 
volved is an extremely difficult one to investigate, and it is 
not surprising that chemists do not agree as to the formula 
to be preferred. 
The simple formula 

H 

He/ \CH 

I I 

JHCv /CH 



H 

leaves the question as to the relation between the carbon atoms 
entirely open, and suffices for most purposes. 

The benzene hypothesis has been treated of somewhat 
fully, for the reasons, that it has played an extremely impor- 
tant part in the study of the benzene derivatives, and that its 
use serves greatly to simplify the study of these derivatives. 

Benzene and its homologues form nitro compounds and sul- 
phonic acids by direct treatment with nitric and sulphuric 
acids, respectively. This distinguishes them from the paraffins 
and other hydrocarbons hitherto treated of. 

Toluene, CtHsC^ CgH 5 . OHs). — Toluene was known before 
it was obtained from coal tar, as it is formed by the dry dis- 
tillation of Tolu balsam, whence its name. Its relation to 
benzene is shown by its synthesis from brom-benzene and 
methyl iodide : — 

C 6 H 5 Br + CH 8 I 4- Na, = C 6 H 3 .CH a + NaBr + Nal 

Note for Student. — Compare this reaction with that used in the syn- 
thesis of ethane from methane, of propane from ethane and methane, etc. 

According to this synthesis, toluene appears as m&hyl-benzme, 
or benzene in which one hydrogen is replaced by methyl; or 
as phenyl-methane, or methane in which one hydrogen atom is 

replaced by the radical phenyl, C e H 6 , which bears the same 
relation to benzene that methyl bears to marsh gas. 



260 XYLENES. 

Toluene is a colorless liquid which boils at 110° ; has the 
specific gravit}' 0.8824 at 0° ; and has a pleasant aromatic 
odor. 

It is very susceptible to the action of reagents yielding a large 
number of substitution-products, some of the most important 
of which will be taken up farther on. 

But one toluene or methyl-benzene has ever been discovered. 

Towards oxidizing agents its conduct is peculiar and interest- 
ing. The methyl is oxidized, while the phenyl remains intact. 
The product is a well-known acid, benzoic acid, which, as we 
have seen, breaks up readily into carbon dioxide and benzene. 
It has the composition C 7 H 6 2 , and is the carboxyl derivative 
of benzene, C 6 H 5 .C0 2 H. The oxidation of toluene is repre- 
sented by the equation 

C 6 H 5 .CH 3 + 3 O = C 6 H 5 .C0 2 H + H 2 0. 

Xylenes, C 8 H 10 [= C 6 H 4 (CH 3 ) 2 ]. — That portion of light oil 
which boils at about 140° was originally called xylene. It 
was afterwards found that this coal-tar xylene consists of 
three isomeric hydrocarbons. As the boiling-points of these 
three substances lie quite near together, it is impossible to 
separate them by means of fractional distillation. By treat- 
ment with sulphuric acid, however, they can be separated, 
and thus obtained in pure condition. They are known as 
ortho-xylene, meta-xylene, and para-xylene. 

Ortho-xylene resembles benzene and toluene in its general 
properties, but boils at 140° to 141°. 

Meta-xylene boils at 137°. 

Para-xylene boils at 136° to 137°. 

These hydrocarbons have also been obtained from toluene by 



BENZENE SERIES OF HYDROCARBONS. 261 

means of the reaction made use of for the purpose of converting 
benzene into toluene : — 

C 6 H 4 <^ H3 + CH 3 I + 2Na = C 6 H 4 <^ 3 +NaBr + Nal. 
Br CH 3 

This sh6ws that they are all methyl-toluenes. There are 
three mono-brom-toluenes, known as ortho-, meta-, and para- 
brom-toluene. For the preparation of ortho-xylene, ortho- 
brom-toluene is used ; meta-brom-toluene yields meta-xylene, 
and para-brom-toluene yields para-xylene. 

Ortho- and meta-xylene have also been obtained from certain 
acids, which bear to them the same relation that benzoic acid 
bears to benzene : — 

rCH 3 
CeHs i CH 3 = C 6 H 4 (CH 3 ) 2 + C0 2 . 
IC0 2 H 

The reaction by which meta-xylene is formed from mesitylenic 
acid is of special importance, as will be pointed out. 

By oxidation, the xylenes undergo changes like that which is 
illustrated in the formation of benzoic acid from toluene, and 
which consists in the transformation of methyl into carboxyl. 

OH 
The first change gives acids of the formula C,IL < 8 , one 

corresponding to each xylene. By further oxidation, these 
three monobasic acids are converted into dibasic acids of the 



CO.,11 

co" 2 i 

of the same kind : 



formula c e fi 4 < pa^- Thus, we have the three reactions, all 



(1) C e H„.CH 8 + 30 = C t .,H,.C(Ul + 11,0 ; 

(2) C e H 4 <^ + 80 = C e H 4 <^ + U.O : 

and (3) C 6 H 4 <^« + 80 - C«< jjgj[ + H a 0. 



262 XYLENES. 

CH 

The three monobasic acids of the formula C 6 H 4 < C q 3 h are 

known as ortho-toluic, meta-toluic, and para-toluic acids re- 
spectively ; and the three dibasic acids obtained from them 
are known as ortlio-phthalic, meta-plitlialic, and para-phthalic 
acids. Starting thus from the three brom- toluenes, we get, 
first, three xylenes, then three toluic acids, and finally three 
phthalic acids. In each case, we distinguish between the 
three isomeric compounds by the prefixes ortho, meta, and 
para. In a similar wa}-, all di-substitution products of ben- 
zene are designated. We therefore have three series into 
which all di-substitution products of benzene can be arranged ; 
and these are known as the Ortho-series, the Meta-series, and 
the Para-series. In arranging them in this way, we may 
select any prominent di-substitution product, and call it an 
ortho compound; and then call one of its isomerides a meta 
compound, and the other a para compound. Having thus a 
representative of each of the three classes, the remainder of 
the problem consists in determining for each di-substitution 
product, by means of appropriate reactions, into which one 
of the three representatives it can be transformed. If from 
a given compound we get the representative of the ortho 
series, we conclude that the compound belongs to the ortho 
series ; if we get the representative of the meta series, we 
conclude that the compound is a meta compound ; and if we 
get the representative of the para series, we conclude that 
the compound is a para compound. As representatives, we 
may select either the three xylenes or the three phthalic 
acids. Now, to repeat, any di-substitution product of ben- 
zene which can be converted into ortho-xylene or into ortho- 
phthalic acid is regarded as an ortho compound, etc. 

This classification of the di-substitution products of benzene 
into the ortho, meta, and para series, by means of chemical 
transformations, is entirely independent of any hypothesis re- 



BENZENE SERIES OF HYDROCARBONS. 263 

garding the nature of benzene. We may now ask, however, 
which one of the three general expressions given above (see for- 
mulas I., II., and III., pp. 256, 257) represents the relation of 
the groups in the ortho compounds, which one the relation in the 
meta compounds, and which one the relation in the para com- 
pounds, ii" we can answer these questions for any three 
isomeric di-substitution products, the answer for the rest will 
follow. To reduce the problem to simple terms, therefore, 
let us take the three xylenes. We have three xylenes and 
three formulas : how can we determine which particular form- 
ula to assign to each xylene? 

As may be imagined, this determination is by no means a 
simple matter ; and it has been the occasion of a great mam- 
investigations. Theoretically, the simplest method available 
consists in carefully studying the substitution-products of each 
xylene, to discover how many varieties of mono-substitution 
products can be obtained from each. The formulas are : — 

OH3 ^Hs ^Hs 

C C C 

{4)llC / X C.CH 3 (4)HC 7 " X CII(1) (4)HC / X CH(1) 

II II I ( 

(3)HCv /CH(1) (3)HC N /CCII, (3)HC X /CH(2) 
\q/ \ q s \ q/ 

H II 

(2) (2) 

Formula I. Formula 11. Formula 111. 



CH 8 



Each of the four unreplaced benzene hydrogens of the xylene 
of formula III. bears the same relation to the molecule. It 
therefore should make no difference which one is replaced, the 
product ought to be the same. This should not be true o\ 
the xylenes represented by formulas I. and 11. Thai xylene, 
whose structure is represented by formula 11 1.. ought therefore 
to yield but one kind oi' mono-substitution product. On stink- 
ing the xylenes, we find the one which boils at 186° to 137°, 



264 ETHYL-BENZENE. 

called para-xylene, yields but one kind of mono- substitution 
products ; that is, we can get from it only one mono-brom- 
xylene ; only one mono-nitro-xylene, etc. We therefore con- 
clude that para-xylene is represented by formula III. above ; 
and, further, that formula III., on p. 257, is the general ex- 
pression for all para compounds. 

Examining formula I., on the preceding page, in the same 
way, we see that H(l) and H(4) bear the same relation to the 
molecule ; and that H(3) and H(2) also bear the same relation 
to the molecule, though different from that of H(l) and H(4). 
Two chlor-xylenes of the formulas 



CH 3 




CH 3 


O 




.C. 


HC X X CCH 3 

1 1 


and 


HC X X C.CH 3 

1 1 


HC X /CC1 

x c x 




x c 7 


H 




€1 



ought to be obtainable from the xylene of formula I. 

In the same way three mono-substitution products should be 
obtainable from the xylene of formula II. The method, the 
principle of which is thus indicated briefly, while theoretically 
simple enough, is very difficult in its application, except in the 
case of the para compounds. Other methods have therefore 
been used, and these will be discussed under mesitylene and 
naphthalene. It may be said, in anticipation, that the result 
of all observations point to formula I. for ortho-xylene ; to 
formula II. for meta-xylene, and to formula III. for para- 
xylene. 

Ethyl-benzene, C 8 H 10 (= C 6 H 5 .C 2 H 5 ). — This hydrocarbon is 
isomeric with the xylenes, but differs from them in that it con- 
tains an ethyl group in the place of one hydrogen of benzene. 



MESITYLENE. 265 

instead of two methyl groups in the place of two hydrogens of 
benzene. It is made by treating a mixture of brom-benzene and 
ethyl bromide with sodium : — 

C 6 H 5 Br + C 2 H 5 Br + 2Na = C 6 H 5 . C 2 H 5 + 2 NaBr. 

Its conduct towards oxidizing agents distinguishes it from the 
xylenes. It yields benzoic acid, just as tolnene does. In this 
case, as in that of toluene, the paraffin radical is converted into 
carboxyl. It has been found that no matter what this radical 
may be, it is, under the same circumstances, converted into car- 
boxyl. Thus, the conversions indicated below take place : — 

C 6 H 5 . CH 3 gives C 6 H 5 . C0 2 H. 

C 6 H 5 .C 2 H 5 « C 6 H 5 .C0 2 H. 

C 6 H 5 .C 3 H 7 " C 6 H 5 .C0 2 H. 

C 6 H 5 .C 5 H n « C 6 H 5 .C0 2 H. 

CeH4< C 2 H 5 C « H4< C0 2 H- 

6 4< C 3 H 7 CoH4< C0 2 H' et °-' etC - 

Mesitylene, C»Hi2[ = Ci;H:;(CH;03]. — Mesitylene is contained 
in small quantity in light oil, and can be obtained in pure con- 
dition from this source. It is most readily prepared by treating 
acetone with sulphuric acid : — 

3 C 3 H (; - (\J I 12 + 3 H 2 0. 

It can also be made by treating methyl-acetylene, CH 3 .C = C 1 1 . 
with sulphuric acid, the action in this case being perfectly an- 
alogous to the polymerisation of acetylene : — 

3CH = CI I :C e H 6 ; 
3C^.C = CH = C fl H 8 (CH 8 )8. 

It is a liquid resembling fche lower members oi' the series in its 
general properties. It boils at l(>o°. 

Its conduct towards oxidizing agents shows that it is a tri- 
methyl-benzene. When boiled with dilute nitric acid, it yields 
mesitylenic avid, (yil 10 O... and uvitic ewt'd, C 8 H 8 4 ; and. by 



266 



MESITYLEKE. 



further oxidation with chromic acid, trimesitic acid, CgH 6 6 , is 
formed. By distillation with lime, mesitylenic acid yields meta- 
xylene and carbon dioxide ; uvitic acid yields toluene and car- 
bon dioxide ; and trimesitic acid yields benzene and carbon 
dioxide. The formation and decomposition of the acids may 
be represented by the equations following : — 



C 6 H 3 (CH 3 ) 3 +30 

Mesitylene. 

rcH 3 

C 6 H 3 j CH 3 +30 
<-C0 2 H 

Mesitylenic acid. 

rcH 3 

C 6 H 3 j C0 2 H +30 
<-C0 2 H 

Uvitic acid. 

rCH 3 
CeH 3 -J CH 3 
(_C0 2 H 

Mesitylenic acid 

rCH 3 
C 6 hJC0 2 H 
(C0 2 H 

Uvitic acid. 

rC0 2 H 

C 6 H 3 ]c0 2 H 
(C0 2 H 

Trimesitic acid. 



rCH 3 

Cq& 3 -j CH 3 + H 2 ; 
IC0 2 H 

Mesitylenic acid. 

(CH 3 
C 6 H 3 ]C0 2 H + H 2 0; 
(C0 2 H 

Uvitic acid. 

f C0 2 H 
C 6 H 3 ]C0 2 H + H 2 0; 
(.C0 2 H 

Trimesitic acid. 

CeH 4 j^ + C0 2 ; 

Meta-xylene. 

C 6 H 5 .CH 3 + 2C0 2 ; 

Toluene. 



C 6 H 6 + 3 C0 2 . 

Benzene. 



These transformations show clearly that mesitylene is tri- 
methyl -benzene, but they do not show in what relation the 
methyl groups stand to each other. 

An ingenious speculation in regard to this relation is based 
upon the fact that mesitylene is formed from acetone. It 



BENZENE SERIES OF HYDROCARBONS. 



267 



appears probable that each of the three molecules of acetone 
taking part in the reaction, 

3 C 3 H 6 = C 9 H 12 + 3 H 2 0, 

undergoes the same change. As the product contains three 
methyl groups, the simplest assumption that can be made is 
that each acetone molecule gives up water as represented 
thus : — 

CH3-CO-CH3 = CH3-C-CH + H 2 0. 

Acetone. 

We thus have three residues, CH 3 — C — CH, and these unite 
to form trimethyl benzene. The only way in which the union 
can be represented, assuming that all three act in the same 
way, is this: — 

CH 3 

HC X X CH 

I I 

H3O.O \ /L/.O-H3 

H 

According to this reasoning, mesitylene is a symmetrical com- 
pound, — that is to say, each of the three methyl groups bears 
the same relation to the molecule ; and the same is true of each 
of the three benzene-hydrogen atoms. 

This view has been tested by replacing the three hydrogen 
atoms successively by bromine; and it has been found thai 
the view is confirmed, as but one mono-bromine substitution- 
product of mesitylene has ever been obtained. Accepting the 
formula above given for mesitylene, an important conclusion 
follows regarding the nature o\' meta-xylene. For we have 
seen that, by oxidizing mesitylene, we get, as the first product, 
mesitylenic acid, — which is mesitylene, one of whose methyls 
has been converted into earboxyl. As all the methyl groups 



268 PSEUDOCUMENE. 

bear the same relation to the molecule, it makes no difference 
which one is oxidized. The acid has the formula 



CH 3 



x cy 

H 



Now, by distilling this acid with lime, carbon dioxide is given 
off, and meta-x3^1ene is produced. 

As the change consists in removing the carboxyl, and replac- 
ing it by hydrogen, it follows that meta-xylene must be repre- 
sented by the formula 

CH 3 

/Cv 

I I 

HC\ /C.CH3 

H 

and consequently that, in all meta compounds, the two substi- 
tuting atoms or groups bear to each other the relation which the 
two methyl groups bear to each other in this formula for meta- 
xylene. 

Pseudocumene, C 9 Hi 2 [=C 6 H 3 (CH3)3]. — This hydrocarbon, 
which is isomeric with mesitylene, occurs in coal-tar oil, from 
which it can be made in pure condition. Its properties are 
similar to those of the lower members of the series. It boils 
at 169.8°. 

Pseudocumene has been made synthetically from brom-para- 
xylene and methyl iodide, and also from brom-meta-xylene and 



BENZENE SERIES OF HYDROCARBONS. 269 

methyl iodide. How this is possible, will be understood by an 
examination of the formulas below : — 

CH 3 CH 3 

HC 7 X CH HC 7 X CH 

II II 

HC X /CBr HC X /C.CH 3 

x cr x cr 

CH Br 

„, 3 , Brom-meta-xvlene. 

Brom-para-xylene. J 

Replacing the bromine by methyl, in either of the compounds 
represented, the product would have the formula 

CH 3 

UC / X CH 

I I 

HC\ /C.CH 3 

9 

CH 3 

which is that of pseudocumene. 

Cymene, \ c l0 H l4 (c«H 4 < CH: 

Para-methyl-isopropyl-benzene, ' \ C ;; H 7 

This hydrocarbon is of special importance and interest, on 
account of its close connection with two well-known groups 
of natural substances, — the groups oi' which camphor and oil 
of turpentine are the best-known representatives. It occurs in 
the oil of caraway and the oil of thyme. The cerpenes, which 
are hydrocarbons of the formula C, IT iri , and o( which oil o\ 
turpentine is the best known, easily give up two hydrogen 
atoms and yield cymene. Probably the simplest way to pre- 
pare cymene is to treat camphor with phosphorus pentasul- 
phide, zinc chloride, or phosphorus peutoxide. 
It is a liquid of a pleasant odor. It boils at 175°, 



270 BENZENE SERIES OF HYDROCARBONS. 

It has been made synthetically from para-brom-toluene and 
isopropyl bromide: — 

C 6 H 4 <£ H3 +C 3 H 7 Br + 2Na 
Br 

= C 6 H 4 <^+2NaBr, 

3 M 7 

which clearly shows its relation to benzene. As the final 
product of its oxidation, it yields para-phthalic (terephthalic) 
acid : — 

see p. 265. 

Hexahydrobenzenes, Naphthenes. 

Caucasian petroleum consists principally of a mixture" of 
hydrocarbons that have been found to be hydrogen addition- 
products of members of the benzene series. They are oils that 
can be converted into members of the benzene series by passing 
them through tubes heated to a red heat. They do not react 
with concentrated nitric or sulphuric acid, and in this respect 
they differ markedly from the benzene hydrocarbons. They 
are called naphthenes. 

CTTo CTT 
Hexamethylene, hexanaphthene, CH2< „ " >CH2. 

CH2 . CH2 

— This is found not only in Caucasian petroleum but in the 
petroleum from other sources. American petroleum contains 
it in small quantity. It can be made artificially by reducing 

iodo-cyclohexane, IHC < CH - 9 ' CH2 > C1X, It is not formed by 
J ' CH 2 .CH 2 " J 

reducing benzene. The product formed when benzene is treated 
with concentrated hydriodic acid is methyl-pentamethylene, 

yCH 2 • CH 2 

CH 3 . CH< I • 

X CH 2 .CH 2 



DIHYDROBENZENES. 271 

Other hydrocarbons of this series are hexahydrotoluene or 

heptanaphthene, CH 3 . CH < 2 ' 2 > CH 2 , hexahydroxylene 

CH 2 • CH 2 

or octonaphthene, (CH 3 ) 2 C fi H 10 , etc. 

Tetrahydrobenzenes. 

The simplest hydrocarbon of this group is tetrahydrobenzene, 
CH 2 . CH 2 . CH 

| || . It is formed from brom-cyclohexane by elim- 

CH 2 . CH 2 . CH 
inating hydrobromic acid from it. 

Tetrahydrotoluene, CH3 . CeHs. is contained in the essence 
of resin. 

Hydrocarbons, OioHis. — There are several hydrocarbons 
of the formula C 10 H 18 known that belong to the series of tetra- 
hydrobenzenes. Among them the following may be men- 
tioned : — 

Hydrocamphene. — This is obtained, together with cam- 
phene, from oil of turpentine by treating the hydrochloride of 
oil of turpentine with sodium. 

Menthene, OHs . CH<^ 2 ' S? ^C. G;Ht. — This is formed 
CHj . CH-: 

from menthol, C^II^O, by treating it with sulphuric acid, phos- 
phorus pentoxide, or anhydrous copper sulphate. 

DlHYDKOBENZENES. 

A number of bhe members of tins group have boon made, as. 
for example, dihydrobenzeno, C, 5 H S , dihydrotoluene, C : ll 10 . di- 
hydroxylenes, C S U,..., etc. 

Dihydro-o-xylene, or canthaiwie, (CH 3 ) 2 C«jH €j is formed by 
heating oantharic acid, C^H^O^ with lime. 



CHAPTER XV. 

DERIVATIVES OP THE HYDROCARBONS, OJfcn-e, 
OF THE BENZENE SERIES. 

Recalling what has been learned under the head of De- 
rivatives of the Paraffins, we should naturally look for repre- 
sentatives of all the classes of compounds there met with. 
The derivatives of the paraffins were classified as : — 

1. Halogen derivatives. 

2. Oxygen derivatives, including the Alcohols, Aldehydes, 

Acids, etc. 

3. Sulphur derivatives, including the Mercaptans, Sulphonic 

Acids, etc. 

4. Nitrogen derivatives, including Cyanides, Amines, Nitro 

compounds, etc. 

5. Metallic derivatives. 

The derivatives of the benzene hydrocarbons may be classi- 
fied in the same way, but a change in the order of treatment 
will be somewhat more convenient, owing to many points of 
analogy that exist between the halogen substitution-products, 
the nitro compounds, and the sulphonic acids. All of these 
three classes of derivatives of the benzene hydrocarbons are 
made by direct treatment of the hydrocarbons with the sub- 
stituting agents, and in some respects resemble one another, 
so that they will be studied in connection. As the amino de- 
rivatives of this series are made almost exclusively from the 
nitro compounds by reduction, they will be taken up in con- 
nection with the nitro compounds ; and, further, by treat- 
ment of the amino compounds with nitrous acid, a new class 



HALOGEN DERIVATIVES OF BENZENE. 273 

of nitrogen derivatives, known as diazo compounds, not met 
with in connection with the paraffins, is formed. These will 
be taken up after the amino compounds. 

After these classes have been studied, the oxygen derivatives, 
which include the phenols or simple hydroxyl derivatives of 
the hydrocarbons, the alcohols, aldehydes, acids, and ketones 
will be taken up in turn ; and, finally, the hydroxy-acids, which 
are strictly analogous to the hydroxy-acids of the paraffin series. 

There are thus the following classes : — 

1. Halogen derivatives. 5. Sulphonic acids. 9. Acids. 

2. Nitro compounds. 6. Phenols. 10. Ketones (and 

3. Amino compounds. 7. Alcohols. Quinones). 

4. Diazo compounds. 8. Aldehydes. 11. Hydroxy-acids. 

The relations of most of these classes to the hydrocarbons 
are the same as those of the corresponding derivatives of the 
paraffin series to the paraffins ; and the general methods of 
preparation, as well as the reactions, are the same. Hence, 
most of the knowledge acquired in the first part of the course 
may be applied to the series now under consideration. 

An enormous number of derivatives of the benzene hydro- 
carbons have been prepared and studied; but only very few 
need to be studied in order to make the chemistry of all of 
them clear. In the following a few of the more important 
representatives of each class will be presented, mainly with 
the object of illustrating general facts and general relations. 

Halogen Derivatives ov Benzene. 

Very little need be said in regard to these derivatives. By 
direct action oi' bromine or chlorine upon benzene the hydrogen 
atoms are replaced one after another, until, as the final products. 
kexarchlor-bemene, C 6 C1 8 , and hexa-bwm-benzene) C«Br a arc ob- 
tained. When the action takes place in direct sunlight, 
addition-products, C 8 H 8 Cl fl and CeH e Br«, are formed. Benzene 



274 DERIVATIVES OF THE BENZENE SERIES. 

hexachloride, C 6 H 6 C1 6 , is formed also when chlorine is con- 
ducted into boiling benzene. The addition-products are de- 
composed, yielding tri-substitution products of benzene and 
halogen acid : — 

C 6 H 6 Br 6 = C 6 H 3 Br 3 + 3 HBr. 

The substitution-products are very stable. They are, as a 
rule, formed more easily than the halogen derivatives of the 
paraffins, and, as a rule, they do not give up the halogens as 
readily. Thus, while it is possible in the paraffin derivatives 
to replace chlorine and bromine by hydroxyl, the amino group, 
etc., these replacements cannot easily be effected in the benzene 
derivatives. The halogens can be removed by sodium, as 
shown in the synthesis of hydrocarbons : — 

C 6 H 5 Br + CH 3 I + 2 Na 
= C 6 H 5 . CH 3 + NaBr + Nal, etc., etc. 

They can also be removed by nascent hydrogen, the hydro- 
carbons being regenerated : — 

C 6 H 4 C1 2 + 4 H = C 6 H 6 + 2 HC1. 

This kind of reverse substitution is not, however, effected 
easily. 

Chlor-benzene, CeHsCl. — Chlor-benzene can be made by 
treating benzene with chlorine, but the action is slow. The 
action is much hastened by adding a little iodine or ferric 
chloride. These substances act as carriers, and are found 
practically unchanged at the end of the operation. Chlor- 
benzene can also be made by boiling a diazonium salt (which 
see) with hydrochloric acid : — 

C 6 H 5 N 2 C1 + HC1 = C 6 H 5 C1 + N 2 + HC1. 

Brom-benzene, CeHsBr. — This is made by the same meth- 
ods as those used in making chlor-benzene. 

Iodo-benzerie ; CeHsI. — This can be made by treating ben- 
zene with iodine and iodic acid : — 



DIBROM-BENZENE. 275 

5 C 6 H 6 4- 41 + HI0 3 = 5C 6 H 5 I + 3H 2 0; 

but it is most easily made through the diazonium salt. It is a 
liquid that solidifies at — 30°. 

Phenyliodoso chloride, CrHs • ICI2. — This compound is 
formed when iodo-benzene in chloroform solution is treated 
with chlorine. When it is treated with caustic potash it is 
converted into iodosobenzene, CeHsIO. This has basic 
properties, and forms salts that are derived from the hypothet- 
ical base, C 6 H 5 I(OH) 2 , as, for example, C fi H 5 I(0 . CO . CH 3 ) 2 . 

Iodoxy-benzene, CeHsIOs, is formed from iodoso-benzene, 
either by heating it alone or by boiling its water solution : — 

2 C 6 H 5 IO = C 6 H 5 I + C 6 H 5 I0 2 . 

Diphenyliodonium Hydroxide, (CcHs)^! • OH. — This re- 
markable substance is formed when a mixture of iodoso- and 
iodoxy-benzene is shaken with silver oxide and water : — 

C 6 H 5 IO + C G H 5 I0 2 + AgOH = (C 6 H 5 ) 2 I . OH + AgI0 3 . 

It is strongly alkaline and forms salts that have many points 
of resemblance with the salts of thallium. 

Diphenyliodonium hydroxide may be regarded as the di- 
phenyl derivative of a hypothetical base, iodonium hydroxide. 
H 2 I(OH), that bears to iodine a relation similar to that which 
ammonium hydroxide bears to nitrogen. Compounds oi' the 
same order are known in which sulphur plays the same part 
that iodine plays in the iodonium compounds, and nitrogen in 
the ammonium com pounds. 

Dibrom-benzene, CcHiBr-j, is one of the products of the 
direct treatment oi' benzene with bromine in the presence oi' a 
carrier. This being a. di-substitution product oi' benzene, it 
follows, from what has been said in regard to isomerism in 
this series oi' hydrocarbons, thai throe isomeric varieties oi' the 
substance ought to be obtainable; and the interesting question 
suggests itself: which one oi' the three possible dibrom-ben- 



276 DERIVATIVES OF THE BENZENE SERIES. 

zenes is formed by direct treatment of benzene with, bromine ? 
The answer to the question is equally interesting. The main 
product of the action is jMra-dibrom-benzene, while there is 
always formed in much smaller quantity some of the ortho 
product. The reason why these products are formed, and 
not the meta compound, is unknown; nor has any plausible 
hypothesis been suggested to account for the fact. 

In studying the substitution-products of benzene, one of 
the first problems that presents itself is the determination 
of the relations which the substituting atoms or groups bear 
to each other. The determination is made, as has been 
stated, by transforming the compounds into others, the rela- 
tions of whose groups are known. Thus, to illustrate, when 
benzene is treated under the proper conditions with bromine, 
two dibrom-benzenes are formed. Without investigation, we, 
of course, cannot tell to which series these compounds belong. 
But, by treating that product which is formed in larger quantity 
with methyl iodide and sodium, we get para-xylene. In other 
words, by replacing the two bromine atoms of the dibrom- 
benzene by methyl groups, we get a compound which we know 
belongs to the para series ; and, therefore, we have determined 
that the bromine product is a para compound. In the follow- 
ing the chief reactions made use of for effecting the trans- 
formations of the derivatives will be discussed. 

Halogen Derivatives of Toluene. 

As toluene is made up of a residue of marsh gas, methyl, 
CH 3 , and a residue of benzene, phenyl, C 6 H 5 , it yields two 
classes of substitution-products : (1) Those in which the sub- 
stituting atom or group replaces one or more hydrogen atoms 
of the phenyl group ; and (2) those in which the substitution 
takes place in the methyl. In general, when treated with 
chlorine or bromine in direct sunlight, or at the boiling tem- 
perature, toluene yields products of the second class ; while, 



HALOGEN DERIVATIVES OF TOLUENE. 277 

when treated in the dark, or at low temperatures, it yields 
products of the first class. Thus, we have the two parallel 
series of chlorine derivatives : — 

i. ii. 

C 6 H 4 C1 . CH 3 . C 6 H 5 . CH 2 C1. 

C 6 H 3 C1 2 • CH 3 . CgHs . CHC1 2 . 

C 6 H 2 C1 3 . CH 3 . C 6 H 5 . CC1 3 . 

When a member of the first class is oxidized, the methyl is 
changed, and the rest of the compound remains unchanged, 
as in the case of toluene. Thus, the first substance of class I. 
yields the product C 6 H 4 C1 . C0 2 H ; the second, C 6 H 3 C1 2 . C0 2 H, 
etc. These products are substituted benzoic acids. On the 
other hand, all the members of the second class yield the same 
product that toluene does ; viz., benzoic acid. Hence, by treat- 
ment with oxidizing agents, it is easy to distinguish between 
the members of the two classes. Further, the halogen atoms 
contained in the methyl react like the halogen atoms in paraffin 
derivatives, while those in the benzene ring do not. When, for 
example, the compound C 6 H 5 .CHC1 2 , which is called benzol 
chloride, is superheated with water, both chlorine atoms are 
replaced by oxygen, the product being the aldehyde ( \ ; I I -, . ( ] I [0, 
which, as we shall see, is the familiar substance, oil of bit- 
ter almonds. When, however, the isomeric di-chlor-toluene 
C G H 3 CL,.C1T 3 is superheated with water, do change takes place. 

Regarding those simple substitution-products of toluene which 
contain one halogen atom in the phenyl, such as mono-brom- 
toluene, C 6 H 4 Br. CH 8 , we see that they are di-substitution prod- 
ucts of benzene, and hence capable of existing in three isomeric 
varieties, ortho, meta, and para. The products formed by 
direct treatment of toluene with chlorine or bromine are mix- 
tures of the para and the ortho compound. 

The determination of the series to which one o( these products 
belongs can be made by replacing the halogen by methyl, and 
thus getting the corresponding xylene. The main product of 



278 DERIVATIVES OF THE BENZENE SERIES. 

the action of bromine on toluene is thus converted into para- 
xylene, and is therefore para-brom-toluene. 

Halogen Derivatives of the Higher Members of 
the Benzene Series. 

Concerning the halogen derivatives of xylene, it need only be 
said that the only one of the three xylenes from which pure 
products can easily be obtained is para-xylene. When this is 
treated with bromine it yields but one mono-brom-xy'lene. The 
significance of this fact has been discussed above. The mono- 
substitution products obtained from the other xylenes are 
mixtures which it is very difficult, and in some cases impos- 
sible, to separate into their constituents. Mesitylene and 
pseudocumene, though both are tri-methyl-benzenes, conduct 
themselves quite differently towards bromine, — the former 
yielding only one mono-bromine product ; the latter, a mixture 
of several. 

Nitro Compounds of Benzene and Toluene. 

In speaking of nitro compounds in connection with the paraf- 
fin derivatives (see p. 100), it was stated that they are obtained 
much more readily from the benzene hydrocarbons than from 
the paraffins. Only a few nitro derivatives of the paraffins are 
known. As will be remembered, they cannot be prepared by 
treating the paraffins with nitric acid, but must be made by 
circuitous methods, the principal one being the treatment of 
the halogen derivatives with silver nitrite : — 

C 2 H 5 Br + AgN0 2 = C 2 H 5 (N0 2 ) + AgBr. 

Nitro-ethane. 

The preparation of a nitro derivative of a hydrocarbon of 
the benzene series is a simple matter. It is only necessary to 
bring the hydrocarbon in contact with strong nitric acid, when 
reaction takes place, and one or more hydrogen atoms of the 



MONO-NITROBENZENE. 279 

hydrocarbon are replaced by the nitro group N0 2 , as repre- 
sented in the equations, — 

C 6 H 6 + HN0 8 - C 6 H 5 . N0 2 + H 2 ; 

C 6 H 5 .N0 2 + HNO3 = C 6 H 4 (N0 2 ) 2 + H 2 0; 

C 6 H 5 .CH 3 +HN0 3 = C 6 H 4 <^ 2 +H 2 0; 

C 6 H 4 < ^ 2 + HNO3 = C 6 H 3 < ^L ^ + H 2 0. 
C±i 3 C±i 3 

The nitro compounds thus obtained are not acids, nor are 
they esters of nitrous acid. If they were esters of nitrous acid 
they would be saponified by caustic alkalies, yielding a nitrite 
and hydroxyl derivatives similar to the alcohols. They do not 
act in this way. When treated with nascent hydrogen they 
are reduced to amino compounds or substituted ammonias. 
Thus, nitrobenzene, C 6 H 5 . N0 2 , gives aniline or amino-benzene, 
C 6 H 5 . NH 2 , which is a substituted ammonia similar to methyl- 
amine and ethylamine. As in these the radical is in com- 
bination with nitrogen, it is probable that the radical is in 
combination with nitrogen in the nitro compounds also, as 
shown in the formula, C 6 H 5 . N0 2 . Everything known about 
these nitro compounds is in harmony with this view. The 
formation of a nitro compound by the action of nitric acid on 
a hydrocarbon is represented thus : — 

C e H 5 H + HO . N0 2 = C 6 ] I, . N 0, + 1 1,0. 

Mono-nitro-benzene, CeHe . NOj. — This substance is made 
by treating benzene with concentrated nitric acid, or with a 
mixture of ordinary concentrated nitric and sulphuric acids. 
In the latter case, the sulphuric acid facilitates the reaction, 
probably by preventing the dilution of the nitric acid by the 
water necessarily formed. 

Experiment r>8. Make a mixture of I60 w ordinary concentrated 
sulphuric acid, and 75 M ordinary concentrated nitric acid. Let it cool 



280 DERIVATIVES OF THE BENZENE SEEIES. 

to the ordinary temperature. Put the vessel containing it in water, 
and add about 15 cc to 20 cc benzene, a few drops at a time, waiting each 
time until the reaction is complete. Shake well until the benzene is 
dissolved ; then pour slowly into about a litre of cold water. A yellow 
oil will sink to the bottom. This is nitro-benzene. Pour off the acid 
and water ; wash two or three times with water ; separate the water 
by means of a pipette, and dry by adding a little granulated calcium 
chloride. After standing for some time, pour off from the calcium chlo- 
ride, and distil from a proper sized distilling-bulb, noting the boiling 
temperature. 

Nitro-benzene is a liquid that boils at 205°, solidifies at 3°, 
and has the specific gravity 1.2. Its odor is like that of the 
oil of bitter almonds, and it is hence used in many cases 
instead of the latter. It is known as the essence of miroane. 
It is manufactured on the large scale, and used principally in 
the preparation of aniline. Its vapor is poisonous. 

Dinitro-benzene, CeHiCNC^) 2. — This is a product of the 
further action of nitric acid on benzene, or on nitro-benzene. 

Experiment 59. Make a mixture of 50 cc concentrated sulphuric 
acid, and 50 cc fuming nitric acid. Without cooling add very slowly 
about 10 cc benzene from a pipette with a fine opening. After the 
action is over, boil the mixture for a short time ; then pour into about 
half a litre of water. Filter off the solid substance thus precipitated, 
press it between layers of filter-paper, and crystallize from alcohol. 

Dinitro-benzene crystallizes in long, fine needles, or thin, 
rhombic plates. Melting-point, 91°. 

By means of two reactions, which will be described under 
the head of Diazo Compounds, it is a simple matter to replace 
the two nitro groups by bromine, thus converting dinitro-ben- 
zene into .dibrom-benzene. When the latter is converted into 
xylene, the product is meta-xylene. Hence, ordinary dinitro- 
benzene is a meta compound. 

Nitro-toluenes, CeHUCNOO-CHs. — When toluene is treated 
with strong nitric acid, substitution always takes place in the 
phenyl. The chief mono-nitro-toluene is a para compound; 



ANILINE. 281 

while, at the same time, a little of the isomeric ortho compound 
is obtained. 

Note for Student. — What mono-bromine products are formed 
by direct treatment of toluene with bromine ? Given a mono-nitro- 
toluene, how is it possible to determine whether it belongs to the 
ortho, the meta, or the para series ? 

By treatment with nascent hydrogen, the nitro-toluenes are 
converted into the corresponding amino compounds, called 
Tohddines (which see). 

Amino Compounds of Benzene, etc. 

The amino derivatives of the paraffins are made, for the most 
part, by treating the halogen derivatives with ammonia : — 

C 2 H 5 Br + NH 3 = C 2 H 5 . NH 2 + HBr. 

In speaking of these derivatives, however, attention was called 
to the fact that they can also be made by treating nitro com- 
pounds with nascent hydrogen. The latter method is one of 
great importance in the benzene series. It is used exclusively 
in the preparation of the amino derivatives of the benzene 
hydrocarbons. Several of these derivatives are well known, 
the simplest and best known being amino-benzene or aniline. 

Aniline, C«H7N( = CoHr, . NH,0. — Aniline was first obtained 
from indigo by distillation. 'Anil is the Portuguese ami French 
name of the indigo plant, and it is from this that the name 
aniline is derived. Aniline is found in coal tar and in bone oil, 
a product, of the distillation el' bones. It is prepared by re- 
ducing nitro-benzene with nascent hydrogen. On the Large 
scale the hydrogen is obtained from hydrochloric acid ami iron. 
For laboratory purposes tin ami hydrochloric acid are perhaps 
best. Other reducing agents, such as an ammoniaeal solution 
of ammonium sulphide, bydriodic acid, etc., also effect the 
ohange, which is represented by the following conation : — 

C,lI A ..NO, + (ni = CJL. Ml, \ '1 110 



282 DERIVATIVES OF THE BENZENE SERIES. 

Experiment 60. Arrange a litre flask with a stopper and a straight 
glass tube from two to three feet long. Put in the flask 85s granulated 
tin and about 400s ordinary concentrated hydrochloric acid. Now add 
slowly 50s nitro-benzene. After the action is over, add enough water to 
dissolve the contents of the flask, then add sodium hydroxide until the 
precipitate first formed is nearly all dissolved. Distil, when aniline 
and water will pass over. Separate as in the case of brom-ethane 
(see p. 30). 

Aniline is a colorless liquid which, soon becomes colored in 
the air. It boils at 182.5°. It solidifies at a low temperature 
and melts at — 8° ; it is easily soluble in alcohol, but slightly 
soluble in water. The solution in water has only a slight alka- 
line reaction. 

Experiment 61. To an aqueous solution of a little of the aniline 
obtained in Exp. 60, in a test-tube, add a filtered solution of bleaching 
powder (calcium hypochlorite). A beautiful purple color is produced. 

To a solution of aniline in concentrated sulphuric acid add a few drops 
of an aqueous solution of potassium bichromate. A blue color is produced. 

The reaction with bleaching powder is due to an impurity 
that is always found in aniline unless it has been specially 
purified. Pure aniline does not give this reaction. 

Aniline bears to benzene the same relation that ethyl-amine 
or amino-ethane bears to ethane. It is a substituted ammonia, 
and, like other bodies of the same class, it unites directly with 
acids, forming salts. Thus, with hydrochloric, nitric, and sul- 
phuric acids the action takes place as represented below : — 

C 6 H 5 .NH 2 + HC1 =(C 6 H 5 .NH 3 )C1; 
C 6 H 5 . M 2 + HN0 3 = (C 6 H 5 . NH 3 ) N0 3 ; 
C 6 H 5 .NH 2 + H 2 S0 4 = C 6 H 5 .NH 3 HS0 4 . - 

The hydrochloride is known in the trade as aniline salt. 

The decomposition of aniline hydrochloride by means of 
a caustic alkali takes place as represented in the following 
equation : — 

C 6 H 5 . NH3CI + KOH = C 6 H 5 . NH 2 + H 2 + KC1. 



DIPHENYLAMINE. 283 

Derivatives of Aniline. — Aniline is much more sensitive 
to the action of reagents than benzene or its halogen or nitro 
derivatives. Substitution takes place easily, but there is danger 
that the aniline will be decomposed by the substituting agent. 
Among the substitution-products that find extensive applica- 
tion is one of the sulphonic acids. 

Dimethyl-aniline, CgHs . N(OHs)2. — When aniline is 
treated with methyl bromide and similar halogen derivatives 
of the paraffins, residues of the paraffins are introduced into 
the aniline in place of the ammonia hydrogen atoms : — 

C 6 H 5 . NH 2 + CH 3 Br = [C 6 H 5 . NHCH 3 ] . HBr ; 
C 6 H 5 . NH 2 + 2 CH 3 Br = [C 6 H 5 . N (CH 3 )J . HBr + HBr. 

Of the compounds obtainable by this method, dimethyl-aniline 
is the most important from the technical point of view. It is 
prepared by a modification of the above method — by heating 
aniline with hydrochloric or sulphuric acid and methyl alcohol 
in a closed vessel : — 

C 6 H 5 . NH 2 . HC1 + CH3OH = C 6 H fi . NH> + CH ;? C1 + H 2 ; 

C 6 H 5 . NH 2 + CH3CI = C 6 H 6 . NH (CH 3 ) . HC1 ; 

C 6 H 5 . NH (CH 3 ) . HC1 + CH 3 OH = C,H 5 . N (CH 3 ) 2 . HC1 + H 2 0. 

It is a liquid that boils at 193°, and solidifies at 0.5°. 

Diphenylamine (CoH,0-NH. — This is another example 
of the possibilities presented by aniline. As will be soon. 
diphenylamine is formed from aniline by the introduction of a 
phenyl group, C 6 IL„ for one o( the ammonia hydrogen atoms. 
It is prepared on the large scale, and finds extensive use in 
the manufacture of dyes. The reaction made use of consists 
in heating aniline with aniline hydrochloride at 200°: — 

C e H 8 .NH a + C 9 H 5 .NH a . HC1 --r (; ll,. MI .r,ll, -f NH 4 C1. 
It is a solid that crystallizes in white laminae from ligroin. 



284 DERIVATIVES OF THE BENZENE SERIES. 

It melts at 54° and boils at 302°. It forms salts with strong 
acids, but these are decomposed by water. 

Acetanilide, CeHs . NH . COCHs. — Aniline reacts with acid 
chlorides as ammonia does. While ammonia forms amides, 
aniline forms anilides. Thus, with acetyl chloride, ammonia 
gives acetamide, and aniline gives acetanilide : — 

CH 3 . COC1 + NH 3 = CH 3 . CONH 2 + HC1 ; 
CH 3 . COC1 + NH 2 . C 6 H 5 = CH 3 . CO . NH . C 6 H 5 + HC1. 

Acetanilide is more easily prepared by heating aniline and 
glacial acetic acid together: — 

CH 3 . COOH + NH 2 . C 6 H 5 = CH 3 . CO . NH . C 6 H 5 + H 2 0. 

Acetanilide crystallizes from water in large, colorless plates. 
It melts at 115° and boils at 304°. It is used in medicine 
under the name antifebrine. 

NH<> 
Toluidines, amino-toluenes, CeH4 < «„ . — The tolui- 

0±±3 

dines, of which there are three corresponding to the three nitro- 
toluenes, are made from the latter in the same way that aniline 
is made from nitro-benzene. As para-nitro-toluene is the best 
known of the three nitro-toluenes, so para-toluidine is the best 
known of the three toluidines. 

The properties of the toluidines are much like those of 
aniline. 

Treated with various oxidizing agents, a mixture of aniline 
and the toluidines is converted into a compound known as 
rosaniline. This is the mother substance of the large group 
of compounds known as the aniline dyes. Rosaniline and its 
derivatives, the aniline dyes, will be treated under Triphenyl- 
methane (which see). 

By nitrous acid the toluidines are transformed in the same 
way that aniline is (see Diazo Compounds). 



DIAZO COMPOUNDS OF BENZENE, ETC. 285 

The xylidines bear to the three xylenes the same relation 
that aniline bears to benzene. It is not a simple matter to get 
any one of them in pure condition. 

Diazo Compounds of Benzene, etc. 

The usual action of nitrous acid on amino compounds is 
represented by the equation, — 

R . NH 2 + HN0 2 = R . OH + H 2 + N* 

When an amino derivative of a hydrocarbon of the benzene 
series is treated with nitrous acid at low temperatures, a prod- 
uct is obtained which contains two nitrogen atoms, and which 
is, therefore, called a diazo compound. Thus, in the case of 
aniline sulphate, the action is represented by the equation, — 

C 6 H 5 NH 2 . H 2 S0 4 + HN0 2 = C 6 H 5 N 2 . HS0 4 + 2 H 2 0. 

Aniline sulphate. Benzene-diazouium sulphate. 

So, also, with the nitrate we have, — 

C 6 H 5 NH 2 . HN0 3 + HN0 2 = C 6 H 5 N 2 . N0 3 + 2 H 2 0. 

Aniline nitrate. Benzene-diazonium nitrate. 

The salts thus formed are called diazonium salts for reasons 
which will presently be given. From them the benzene-diazo- 
nium hydroxide itself cannot be set free. 

Experiment 62. Arrange an apparatus as shown in Fig. 11. In 
flask A put arsenic trioxide (about 608), ami through the funnel-tube 
pour 40 co to 50 eo ordinary nitric acid (sp. gr. L85). 5 is an empty cylin- 
der surrounded by water. C is a test-tube of about 50 00 rapacity, tn 
it should be brought LOs aniline nitrate, and 12°° ice-cold water. This is 
placed in ice water. Pass a ourrenl of the oxides of nitrogen until the 
material in the tube dissolves. Add to the solution about an equal 
volume of alcohol previously cooled to 0°, and then a little eold ether. 
if the operation has been successful, a copious precipitate of crystals 
of benzene-diazonium nitrate will appear. Filter o\\ with the aid of a 
SUCtion-pump, and, Without delay, proceed to study the properties of the 
compound. 



286 



DERIVATIVES OF THE BENZENE SERIES. 



(a) Dissolve a little in water of the ordinary temperature, and allow 
the solution to stand. Decomposition, indicated hy change of color, will 
take place. 

(6) Boil a little with water in a test-tube, and notice the odor of 
phenol or carbolic acid. 




Fig. 14. 



(c) Boil a few grams with alcohol in a test-tube, and notice the ease 
with which the decomposition takes place. The chief product is ethyl- 
phenyl ether or phenetol, C 6 H 5 j O . C 2 H 5 . 

(d) Boil some with concentrated hydrochloric acid. Chlor-benzene is 
formed, which sinks to the bottom when water is added. 

In all these experiments a gas is evolved which can be shown to 
be nitrogen. Collect some, and show that it does not support com- 
bustion. 

(<?) Place a very little of the compound, dried by pressing in 
filter-paper, on an anvil, and strike it sharply with a hammer. It 
explodes. 

The above experiments serve to indicate the instability of 
benzene-diazonium nitrate. This same instability is character- 
istic of all diazonium salts, and it is the ease with which they 



DIAZO COMPOUNDS OF BENZENE, ETC. 287 

undergo a variety of changes that makes them so valuable. 
The principal changes are : — 

1. That illustrated in Exp. 62 (&), which is brought about 
by boiling with water. The action is represented thus : — 

C 6 H 5 ]Sr 2 . N0 3 + H 2 = C 6 H 5 . OH + N 2 + HN0 3 . 

Phenol. 

2. That illustrated in Exp. 62 (c), which is effected by boil- 
ing with alcohol : — 

C 6 H 5 N 2 . N0 3 + C 2 H 5 . OH = C 6 H 5 . . C 2 H 5 + N 2 + HN0 3 . 

Phenetol. 

In some cases alcohol reacts in another way, thus : — 

EN 2 C1 + C 2 H 5 OH = M + N 2 + C 2 H 4 + HC1. 

The result of this is the substitution of hydrogen for the 
diazo group. Sometimes both reactions take place with alcohol. 

3. That effected by hydrochloric acid as illustrated in Exp. 
62(d): — 

C 6 H 5 N 2 . N0 3 + HC1 = C 6 H 6 C1 + N 2 + HN0 3 . 

Mono-chlor-benzene. 

This reaction is much facilitated by cuprous chloride (Sand- 
meyer's reaction). 

Changes similar to the last are effected by hydrobromic and 
hydriodic acids, the chief products being brom-benzene and 
iodo-benzene respectively. Here also the corresponding cu- 
prous salts are of great assistance. 

From the above it follows that, if we have a compound con- 
taining a nitro group, we can. by making the diazonium salt. 
transform it (1) into the corresponding hydroxy] derivative; 
(2) into the corresponding chlorine, bromine, or iodine deriva- 
tive; or, (3) we can make ethers containing such groups as 
CjlI,,Oi CH 8 0, etc. These reactions involving the use of the 
diazonium salts have been used very extensively in the inves- 
tigation of the substitution-products of the benzene series. 

Note fob Student. - llow oan the relation of the croups in dinitro 

benzene be determined bv using the dia. ouium reactions ? 



288 DERIVATIVES OF THE BENZENE SERIES. 

Constitution of the Salts of Diazo Compounds. — The 

salts formed by the action of nitrous acid on aniline salts are 
salts of a strong base which is to be compared with the alkali 
salts. It has been shown by determinations of the freezing 
point and of the electrical conductivity of the solutions of 
these salts in water that they are broken down into ions in the 
same way as salts of strong bases. This suggests that they 
are analogous to ammonium salts, and the view that is most 
in accordance with all the facts is that represented by such 
formulas as the following : — 

C 6 H 5 . N - CI C 6 H 5 . N - N0 3 C 6 H 5 - N - HS0 4 

111 III III 

N N N 

As the salts are analogous to ammonium salts, they are called 
diazonium salts. According to this view they are to be regarded 
as aniline salts into which a nitrogen atom has been introduced 
in place of three hydrogen atoms : — 

C 6 H 5 -N-C1 — ^ C 6 H 5 -N-C1; 

III III 

H 3 N 

C 6 H 5 -N-N0 3 — ^ C 6 H 5 -N-N0 3 . 

Ill III 

H 3 N 

Metallic Derivatives of Diazo-benzene and of Isodiazo- 
benzene. — When a diazonium salt is treated in the cold with 
caustic potash a potassium salt of the formula C 6 H 5 . N 2 . OK is 
formed. When this is treated with ethyl iodide it gives an 
ether of diazo-benzene, C 6 H 5 . N 2 . OC 2 H 5 . The fact that the 
ethyl in this compound is in combination with oxygen is shown 
by its decompositions. It does not yield ethylamine as it would 
if the ethyl were in combination with nitrogen. When the 
above-mentioned potassium salt is treated with phenols (which 
see) it reacts with them at once, forming azo compounds (which 
see). 



METALLIC DERIVATIVES OF DIAZO-BENZENE. 289 

When the ordinary potassium salt of diazo-benzene is heated 
with concentrated caustic potash at 130°, it is converted into 
iso-diazo-benzene potassium without change of decomposition. 
This new salt does not react with phenols, and with ethyl 
iodide it gives a compound in which the ethyl is in combina- 
tion with nitrogen. It is a nitroso compound of the formula 

The facts above stated suggest that the ordinary or normal 
diazo-benzene potassium has the structure represented by the 
formula C 6 H 5 — N 2 — OK, and that iso-diazo-benzene potassium 
has the formula C 6 H 5 — NK . NO, and that they correspond to 
the two diazo-benzenes : — 

C 6 H 5 . N 2 . OH C 6 H 5 . NH . NO 

Diazo-benzene. Iso-diazo-benzene. 

These formulas do not, however, appear probable in view of 
other facts. 

It has been suggested that the two potassium salts and 
other similar salts are stereoisomeric, as represented in the 
formulas : — 

C (5 H 5 -N C 6 H 5 -N 

II II 

KO . N N . OK 

Diazo-benzene potassium. [so-diazo-benzene potassium. 

By way of explanation of these formulas, it should be said 
that they involve^ the conception that the nitrogen atom exerts 
its affinities in the direction of three edges of a tetrahedron, 

thus : — 




When combined with another nitrogen atom by double union 
the figures representing this condition would be: — 



290 DERIVATIVES OF THE BENZENE SERIES. 

X*: X X ^x 





or 



There are two ways in which the groups or atoms X and Y 
can be arranged in space, or there should be two isomeric forms 
of compounds containing a group of two nitrogen atoms of the 
form — X = X — . 

Diazo-amino Compounds. — When a diazonium salt reacts 
with an amino compound a diazo-amino compound is formed, 
as, for example, when benzene-diazonium chloride acts upon 
aniline : — 

C 6 H 5 . X 2 C1 + XH 2 . C 6 H 5 = C 6 H 5 X 2 . XH . C 6 H 5 + HC1. 

As will be seen, the residue of the diazonium salt takes the 
place of one of the hydrogen atoms of the amino group. Diazo- 
amino-benzene forms golden yellow laminae or prisms. It is 
insoluble in water, but readily in hot alcohol. When heated 
with aniline it is transformed into amino-azo-benzene : — 

C 6 H 5 . X 2 . XH . C 6 H 5 -^ C 6 H 5 . X 2 . C 6 H 4 . XH 2 . 

Other diazo-amino compounds act in the same way. The 
product formed in the above case is an amino derivative of 
a compound of the formula C 6 H 5 . X 2 . C 6 H 5 , known as azo- 
benzene. 

Azobenzene, C6H5 . N2 . CeHs, is formed by partial reduc- 
tion of nitro-benzene in alkaline solution, as by treating with 
an alcoholic solution of caustic potash. It crystallizes from 
alcohol in orange-red, rhombic crystals. Reducing agents 
convert it into hydrazo-benzene, C 6 H 5 . XH . XHC 6 H 5 . Azo com- 
pounds are, in general, highly colored, and many of them are 



REDUCTION-PRODUCTS OF NITROBENZENE. 291 

used as dyes. Those that are useful in this way are deriva- 
tives of the simple azo compounds, especially those containing 
the sulphonic acid group, S0 3 H. Some of them will be men- 
tioned in other connections. 

Hydrazo-benzene, CeHs . NH . NH . CgHs, is formed by re- 
duction of azo-benzene. It is made by reduction of nitro- 
benzene by means of zinc dust in alkaline solution, without 
isolating the azo-benzene which is formed as an intermediate 
product. It forms colorless laminae, is scarcely soluble in 
water, but easily in alcohol and ether. Under the influence 
of mineral acids, hydrazo-benzene is transformed into the iso- 
meric benzidine, 

C 6 H 4 .M 2 

I 

C 6 H 4 .NH 2 : 

C 6 H 5 .M C 6 H 4 .NH 2 

C 6 H 5 .NH C 6 H 4 .NH 2 . 

Hydrazo-benzene. Benzidine. 

Reduction-products of Nitro-benzene. — The final re- 
duction-product of nitro-benzene is ammo-benzene or aniline. 
but by regulating the conditions, a number of intermediate 
products can be obtained. In addition to those already men- 
tioned there are two others, azoxy-berusene, C 6 H 5 . X..0 . C 6 H a and 
phenyl-hydroxylamine, C e H 6 . NH (OH). 

The following table will serve to emphasize the relations be- 
tween most of these products : — 

0,11,. N0 2 C„H,.Nv C 6 H 8 .N (Y.II-.XH 0,11-,. Ml 
I >0 || | 

(\ ; ir,.N/ (\;H,.N 0,11,. Nil 

Nitro-benzene. Axoxy-bemene. \ o-beniene, Sydraso*beniene, Aniline. 

These compounds are representatives o\' classes o\' similar 
structure and properties. 



292 DERIVATIVES OF THE BEXZEKE SERIES. 



Hydrazines. 

Hydrazo-benzene is a derivative of hydrazine, NH 2 . NH 2 , and 
may be called symmetrical diphenylhydrazine in view of the 
fact that the two phenyl groups contained in it are symmetric- 
ally distributed, as shown by the formula, C 6 H 5 . NH . NH . C 6 H 5 . 
The simplest representative of the class of aromatic hydrazines 
is phenylhydrazine, C 6 H 5 . 1STH . NH 2 , a compound which, as 
has been seen, has played an important part in the investiga- 
tion of the sugars. 

Phenylhydrazine, CeHs . NH . NH2. — This is formed by 
the reduction of diazonium salts : — 

C 6 H 5 . N 2 C1 + 4 H = C 6 H 5 . NH . NH 2 . HC1. 

Benzene diazonium chloride. Phenylhydrazine hydrochloride. 

It forms crystals that melt at 23°. It boils at 242°. It finds 
extensive application in connection with the manufacture of 
antipyrine (which see). 

Phenylhydrazine is a monacid base, and forms well-charac- 
terized salts. It reacts with aldehydes and with ketones, 
forming hydrazones (see page 190). 

Stjlphonic Acids of Benzene, etc. 

The methods of preparation of the sulphonic acids, and the 
relations of these acids to the hydrocarbons, were pretty fully 
discussed in connection with the paraffins. Three general 
methods for their preparation were given. These are: — 

1. Oxidation of the mercaptans ; thus, ethyl-sulphonic acid 
is formed by oxidation of ethyl-mercaptan : — 

C 2 H 5 . SH + 3 = C 2 H 5 . S0 3 H. 

2. Treatment of a halogen substitution-product with a sul- 
phite, — C 2 H 5 Br + Na 2 S0 3 = C 2 H 5 . S0 3 Na + NaBr. 

3. Treatment of a hydrocarbon with sulphuric acid, This 



BENZENE-SULPHONIC ACID. 293 

method is not applicable to the paraffins, bnt is the one used 
almost exclusively in the case of the benzene hydrocarbons. 
This reaction is characteristic of the aromatic compounds. 
Benzene-sulphonic acid is formed thus : — 

C 6 H 6 + H 2 S0 4 = C 6 H 5 .S0 3 H + H 2 0. 

Toluene- sulphonic acid is formed thus : — 

C 6 H 5 .CH 3 + H 2 S0 4 = C 6 H 4 <^L + H 2 0. 

The reasons for regarding the sulphonic acids as sulphuric 
acid in which hydroxyl is replaced by radicals, were given on 
p. 76 ; and the student is advised carefully to re-read what 
is there said. 

Benzene-sulphonic acid, C (i H (i S0 3 f = §^ 5 } S0 2 Y — This 

acid is made by treating benzene with sulphuric acid. Simi- 
larly, and more easily, toluene- sulphonic acid, C 7 H 7 .S0 3 H, is 
made from toluene. 

Experiment 63. In a flask bring together about 50 cc toluene and 
100 cc concentrated sulphuric acid (ordinary). Heat on a water-bath 
and shake until most of the toluene is dissolved. Pour the contents 
of the flask into a large evaporating dish of at least 8 1 to 10 1 capacity, 
containing 4 1 to 5 1 water. Heat gently, and add gradually, stirring 
meanwhile, finely-powdered chalk, until the solution has become neu- 
tral. Pass through a muslil) Alter attached to a wooden frame, and 
wash thoroughly with hot water. Afterwards retilter the tilt rate 
through a paper filter. Evaporate to quite a small volume (say f>0i> v 
to 70O' 1 '), and tiller from gypsum. In solution there is now the cal- 
cium salt of the sulphonic acid. Add just enough of a solution of 
sodium carbonate to precipitate exactly the calcium; filter off from 
the calcium carbonate, ami evaporate to dryness, finally, OD the water- 
bath. To prevent caking it is necessary to stir the thick, syrupy mass. 
When it Is nearly dry, it is best to powder it. and complete the drying 
at 100° to L20° in an air-bath. The sodium salt can be used for B 
number of experiments. 



294 TOLTTENE-SULPHONIC ACID. 

Experiment 64. In a dry evaporating dish mix thoroughly 20s of 
sodium toluene-sulphonate with 25s of phosphorus penta-chloride, by 
means of a dry pestle. The mass becomes semi-liquid and hot, and 
hydrochloric acid is given off, in consequence of the action of the 
moisture of the air on the chlorides of phosphorus. Hence, the experi- 
ment should be performed under a hood or out of doors. The reaction 
which takes place is represented by the equation, — 

C 7 H 7 .S0 2 ONa + PC1 5 = C 7 H 7 .S0 2 C1 + POCl 3 + NaCl. 

After the action is over, and the mass cooled down to the ordinary 
temperature, add about a litre of cold water. Everything will dissolve 
except the sulphon-chloride, C 7 H 7 . S0 2 C1, which will remain as a heavy 
oil at the bottom of the vessel. Pour off the water, add about 500 cc of 
Strong ammonia, and let stand. The chloride will thus be converted 
into the corresponding sulphon-amide, thus : — 

C 7 H 7 . S0 2 C1 + 2 NH 3 = C 7 H 7 . S0 2 NH 2 + NH 4 C1. 

After cooling, filter off the sulphon-amide ; wash well with cold water, 
and crystallize from water. 

Note for Student. — Refer back to what was said regarding the 
acid chlorides and acid amides, paying particular attention to the 
general methods of preparation and their decompositions. 

Experiment 65. Mix 20= potassium cyanide with an equal weight 
of dry potassium toluene-sulphonate, and distil from a small retort. 
The distillate is impure tolyl cyanide, C 7 H 7 . CN : — 

°KO > S ° 2 + KCN = ^ ' CN + K * S0 »' 

Put the tolyl cyanide in a flask of 300 cc to 400 cc capacity, and add a mix- 
ture of 50 cc water and 150 cc ordinary concentrated sulphuric acid. Heat 
on a sand-bath until the toluic acicl begins to appear in the form of fine, 
white needles in the neck of the flask. On cooling, the acid will crys- 
tallize out. Pour off the liquid, and wash with cold water. Now 
crystallize the acid once or twice from water. When pure, para- 
toluic acid melts at 177°. The reaction is represented by the fol- 
lowing equation : — 

C 7 H 7 .CN + 2 H 2 = C 7 H 7 .C0 2 H + NH 3 . 
Benzene-sulphonic acid itself is a very easily soluble sub- 



SULPHANILIC ACID. 295 

stance. It is a strong acid, and yields a series of salts and 
other derivatives. 

When fused with potassium hydroxide, benzene-sulphonic 
acid is converted into phenol (Exp. 66, p. 298) : — 

C 6 H 5 . S0 3 K + KOH = C 6 H 5 . OH + K 2 S0 3 . 

By further treatment of benzene with fuming sulphuric acid 
a benzene-disulphonic acid is formed. This is capable of the 
same transformations as the mono-sulphonic acid. 

Note for Student. — By what reaction could benzene-disulphonic 
acid be transformed into the corresponding dicarbonic acid, C6H 4 (C0 2 H)2 ? 
Suppose the product obtained were meta-phthalic acid, what conclusion 
could be drawn with reference to the relation of the two sulpho groups, 
SO3H, in the disulphonic acid ? 

NH2 
Sulphanilic acid, C 6 H4 < ~^ _. — When aniline is treated 

1303x1 

with concentrated sulphuric acid, aniline sulphate, C 6 H 5 NH 3 . 

HSO4, is first formed. Further action converts this into the 

NH 
para-sulphonic acid, C (i H 4 < * : 

S0 8 H(p) 

C 6 H 5 . NH 3 . HS0 4 = C 6 H 4 < ™L + H 2 0. 

oU 3 xl 

Sulphanilic acid is difficultly soluble in cold water, more easily 
in hot water. It crystallizes from a solution in water in 
rhombic plates. 

Like taurine (which see) it is probably an "inner salt." ami 

should, therefore, be represented by fche formula (\;ll,^ 8 >. 

SO : 

11 is, however, a strong acid, while taurine is neutral. This 
is accounted for by the fact that aniline LS a much weaker base 
than ethylamine. In taurine the basic portion has the power 
to neutralize the acid portion, while in sulphanilic acid this is 
not the ease. Sulphanilic acid timls extensive application in 
the manufacture oi' dyes. 



296 DERIVATIVES OF THE BENZENE SERIES. 

Helianthin, methyl orange, tropaeolin D, is an example 
of the azo dyes already referred to. It is formed by the action 
of diazobenzene-sulphonic acid on dimethyl-aniline. The diazo- 
benzene-sulphonic acid is made from sulphanilic acid : — 

(1) C 6 H 4 <^> _ CA<* > 

Sulphanilic acid. Diazobenzene-sulphonic acid. 

(2) C 6 H 4 < *f» > + C 6 H 5 . N(CH 2 ) 2 = C 6 H 4 . N 2 . C 6 H 4 . K(CH 3 ) 2 

feU 3 J 

S0 3 H 

Diazobenzene-sulphonic Dimethyl- Dimethyl-aniline-azo-benzene- 

acid. aniline. sulphonic acid. 

The product here represented is methyl-orange. It is not 
used as a dye, though it has marked coloring power. 

Diphenylamine orange, tropseolin OO, is another ex- 
ample of the azo dyes. It is made by the action of diazotized 
sulphanilic acid on diphenyl-amine : — 

C 6 H 4 <?"*> + ^ 5 > NH = C 6 H 4 . K 2 . C 6 H 4 . NH . C 6 H 5 . 

S0 3 H 

The sulphonic acid thus formed is the acid of which diphenyl- 
amine orange is the sodium salt. 



Phenols, or Hydroxyl Derivatives of Benzene, etc. 

The hydroxyl derivatives of the paraffins are called alcohols. 
As will be remembered, they are of three kinds, each of which 
is characterized by certain properties. These are : — 

1. Primary alcohols, of which ordinary ethyl alcohol is the 
commonest example, and which, when oxidized, yield aldehydes 
and then acids containing the same number of carbon atoms. 

2. Secondary alcohols, which by oxidation yield acetones and 
then acids containing a smaller number of carbon atoms. 



PHENOLS. 297 

3. Tertiary alcohols, which by oxidation yield neither alde- 
hydes nor acetones, but break down at once, yielding acids 
with a smaller number of carbon atoms. 

The primary alcohols were shown to correspond to the 

rn rn 

TT T> 

formula C < ; the secondary to C < ; and the tertiary to 
I HO I HO 

C < ; or, in other words, the primary alcohols contain the 

I HO 

group CH 2 .OH; the secondary, the group CH.OH; and the 
tertiary, the group C . OH. 

Now, the simplest hydroxyl derivative of the members of 
the benzene series is phenol, C 6 H 5 . OPI, or t enzene in which 
one hydrogen is replaced by hydroxyl. Representing this com- 
pound in terms of the accepted benzene hypothesis, we have 
the formula 

OH 

/ C \ 

HCT X 0H 

I I 

HC \ / GH 

II 

According to this, phenol appears to be allied to the tertiary 
alcohols, as it contains the group C.OH, and not CH.,011 nor 
(MI. OH. We shall see thai, in fact, phenol conducts itself 
towards oxidizing agents like the tertiary alcohols. 1 1 yields 
neither aldehydes nor ketones. 

All compounds which contain hydroxy 1 in the place of the 
benzene-hydrogen atoms of benzene and its homologues are 
called phenols. As in the case of alcohols, there are phenols 
containing one hydroxyl, or mon-acid phenols ; those containing 



298 DERIVATIVES OF THE BENZENE SERIES. 

two hydroxyls, or di-acid phenols ; those containing three hy- 
droxyls, or tri-acid phenols, etc. Some of these are familiar 
substances. 

Mon-acid Phenols. 

Phenol, carbolic acid, CeHeOCCeHsOH) — Phenol is found 
in small quantities in the urine. It is formed by the distilla- 
tion of wood, coal, and bones. Hence, it is a constituent of 
coal tar, and from this it is prepared. For this purpose the 
heavy oil (see p. 250) is treated with an alkali which dissolves 
the phenol. From the solution it is precipitated by hydro- 
chloric acid. It is puriL .,u. by distillation. 

Phenol can also be made by converting nitro-benzene into 
aniline; then into diazo-benzene, and boiling this with water 
(see Exp. 62 (&)) , and by melting benzene-sulphonic acid with 
potassium hydro dde. 

Experiment 66. In a silver (or iron) crucible, or evaporating dish, 
melt 40s to 50s potassium hydroxide, after adding a few cubic centimetres 
of water. Now add gradually 10s finely-powdered sodium toluene-sulpho- 
nate, obtained in Exp. 63, stirring constantly with a silver (or iron) spatula. 
Do not heat to a very high temperature. After the mass has been kept in 
a state of fusion for one-quarter to one-half an hour, let it cool. Dissolve 
in 200 cc to 250 cc water, and acidify with hydrochloric acid. Notice the 
odor of the gases given off. What gas do you detect ? When the liquid 
has cooled down, extract with ether in a glass-stoppered cylinder. From 
the ether extract distil the ether on a water-bath. The residue is impure 
cresol (p. 303). Phenol can be detected by the following reactions, for 
which a solution in water should be prepared : — 
t (a) A few drops of ferric chloride solution gives a beautiful blue color. 
(&) Add one-fourth volume of ammonia, and then a few drops of a 
dilute solution of bleaching powder. A blue color is produced. 

(c) Bromine water gives a yellowish-white precipitate of tri-brom- 
phenol. 

The reaction which takes place in melting potassium hydrox- 
ide and potassium benzene-sulphonate together is represented 
by the equation, — 



METHYL-PHENYL ETHER. 299 

C 6 H 5 . S0 3 K + KOH = C 6 H 5 . OH + K 2 S0 3 . 

It effects the replacement of the sulpho group, S0 3 H, by 
hydroxyl. Phenol is made by this method on the large 
scale. 

Phenol, when pure, crystallizes in beautiful colorless rhombic 
needles. The presence of a little water prevents it from solidi- 
fying. It has a peculiar, penetrating odor; boils at 180°; is 
difficultly soluble in water (1 part in 15 parts water at ordinary 
temperature) ; mixes with alcohol and ether in all proportions ; 
and is poisonous. It is a valuable antiseptic, and finds exten- 
sive application as a disinfectant and in the manufacture of 
picric acid. 

A dilute solution of phenol is colored violet by a little ferric 
chloride. 

Bromine water gives a precipitate of tri-brom-phenol when 
added to a water solution of phenol. 

Phenol is not soluble in alkaline carbonates. Its acid proper- 
ties are not strong enough to enable it to decompose these 
carbonates. On the other hand, it forms salts with the alkalies 
and with several strong bases. Among these may be mentioned 
the following : — 

Potassium phenolate, C (J H 5 . OK, made by dissolving potassium 
in phenol, and by treating phenol with a solution of caustic 
potash. 

Ban' ion phenolate, (C 6 H 8 0) 2 Ba + 2 H 2 0, made by dissolving 
phenol in baryta water. 

Lead oxide phenol, C 6 H 6 O.PbO, made by dissolving load 
oxide in phenol. 

Phenol also forms ethers, of which the methyl, ethyl, and 
diphenyl ethers may serve as examples: — 

Methyl-phenyl ether, OtHsO (25^ > OV— This sub- 

VCH 1 

stance, also called anisol, is obtained from anisic acid 
(methoxy-benzoic aoid) by boiling with baryta water. It is 



300 DERIVATIVES OF THE BENZENE SERIES. 

made also by treating potassium phenolate, C c H 5 OK, with 
methyl iodide : — 

C 6 H 5 OK + CH 3 I = ^ > + KL 

It is a liquid of a pleasant odor. 

Note for Student. — Compare this substance with ordinary ether. 
What method analogous to that above mentioned can be used in the 
preparation of ordinary ether ? 

Ethyl-phenyl ether, CsHioO ( %^ 5 > o), is called jrfienetol 

VO2H5 / 

Diphenyl ether, C12H10O (2 6 S 5 > oV — This bears to 

VOeHo / 

phenol the same relation that ordinary ether bears to alcohol. 
With acids, phenol, like the alcohols, yields ethereal salts in 
which the phenyl group, C 6 H 5 , takes the place of a metal. 
Among the compounds of this class which phenol forms with 
organic acids, the following may be mentioned : — 

Phenyl acetate, C 8 H 8 2 (= CHs . CO2 . C 6 H 5 ). — This is 
formed by treating phenol with acetyl chloride. 

Note for Student. — What use is acetyl chloride put to as a reagent 
in organic chemistry ? Explain its use. What conclusion can be drawn 
from the fact that acetyl chloride acts upon phenol, replacing one hydrogen 
by acetyl, C 2 H 3 ? 

Substitution-products of phenol. Phenol is very susceptible 
to the action of various reagents, and a large number of substi- 
tution-products have been made from it. 

Bromine acts upon it readily. If, for example, bromine water 
is added to a water solution of phenol, tri-brom-phenol is formed 
and precipitated. 

Dilute nitric acid acts upon phenol, yielding two mono-nitro- 

phenols, C 6 H 4 j i-J 2 , one of which has been shown to belong to 
the ortho series, the other to the para series. 



TRI-NITKOPHENOL, PICRIC ACID. 



301 



Experiment 67. Add 20e phenol to a mixture of 80 cc water and 
40 cc ordinary concentrated nitric acid (sp. gr. 1.34). Stir, and, after a 
time, pour off the dilute acid from the oil. Wash with water, and then 
put it into a flask, with about a litre of water, arranged as shown in 
Fig. 15. Flask A holds nothing but water ; while the oil, together with 




Fig. 15. 

water, are in B. From A a current of steam is passed into B, which is 
heated by means of a lamp. Yellow crystals pass over and appear in the 
receiver, while a non-volatile substance remains behind in flask B. The 
volatile substance is ortho-nitro-phenol ; the non-volatile is para-nit ro- 
phenol. 

f s (NO*) 

Tri-nitro-phenol, picric acid, CcHsNsOtI CeHa < qjj 

This is formed very easily by the action of strong nitric acid 
on phenol. 

Experiment (>8. Add 10- phenol slowly to 10« concentrated nitric 
acid. When the action is over, add 808 fuming nitric acid and boil for 
some minutes. Extract the picric acid by means of hot water, and purify 
by dissolving in potassium carbonate, and evaporating to crystallization. 

Picric acid crystallizes in yellow Leaflets or prisms, has a 

very bitter taste (whence the name, from ruepos, bitter), is 

poisonous, decomposes with explosion when heated vapidly. 
It dyes wool and silk yellow. 



302 DERIVATIVES OF THE BENZENE SERIES. 

Note for Student. — Is there any analogy between tri-nitro-phenol 
and tri-nitro-glycerin ? "What is the essential difference between them ? 

It is extensively used as an explosive under the name lyddite. 

One of the most interesting properties, of tri-nitro-phenol is 
its power to form salts. It acts like a strong acid. It will 
thus be seen that, while the substance C 6 H 5 . OH has only very 
slight acid properties, the same substance, with three of its 
hydrogens replaced by nitro groups, C 6 H 2 (N0 2 ) 3 . OH, has 
strong acid properties. In the salts, which have the general 
formula C 6 H 2 (N0 2 ) 3 . OM, the metals replace the hydrogen of 
the hydroxy 1. Among them may be mentioned the potassium 
salt which was obtained in Exp. 68 ;• this explodes when heated 
and when struck., Ammonium picrate, C 6 H 2 (N0 2 ) 3 . ONH 4 , is 
used as a constituent of explosives. 

Aminophenols, CeH4 < ™" ■ — The aminophenols are 

NH2 

formed by reducing the nitrophenols by means of tin and 
hydrochloric acid. Metaminophenol and some of its deriva- 
tives are used in the preparation of the rhodamine dyes. 

Paraminophenol, a solid that melts at 184°, yields an ethyl 

OP TT 

ether, p-phenetidine, C 6 H 4 < ATTT 2 5 . This ether is converted by 

NH2 

glacial acetic acid into an acetyl derivative of the formula, 

OC 1 H 
C 6 H 4 <. TrT 2 JL __ . This is sometimes called acetaminophenetol. 

NH . CO . CH3 

It is extensively used in medicine under the name phenacetin. 
Phenolsulphonic acids, OeH*< ~~ . — When phenol is 

treated with sulphonic acid, the ortho and para sulphonic acids 
are formed. At low temperatures the ortho acid is formed in 
larger quantity than the para acid. The ortho acid is readily 
converted into the para acid by heat, so that, at a compara- 
tively high temperature, the para acid is the principal product. 
The change of the ortho acid to the para takes place even when 
its water solution is boiled. Orthophenolsulphonic acid is used 
in water solution as an antiseptic under the name aseptol. 



CKESOLS. 303 



|o« 



Phenyl-mercaptan, 

Phenyl hydrosulphide, [-CeHeSCCcHs . SH). - 

Thiophenol, 

the same relation to phenol that mercaptan bears to alcohol. 
It can be made by reducing benzene-sulphonic acid. This 
reduction is effected by first making the sulph on-chloride, 
C 6 H 5 . S0 2 C1 (Exp. 64), and then treating this with nascent 
hydrogen. 

Note for Student. — What is the effect of oxidizing the mercaptans ? 

It can be made, also, by treating phenol with phosphorus 
pentasulphide, the effect of this reagent being to substitute 
sulphur for oxygen. 

Note for Student. — What analogy is there between the action of 
phosphorus pentachloride and of phosphorus pentasulphide on compounds 
containing oxygen ? 

Phenyl-mercaptan is a liquid, with a very disagreeable odor. 
It forms a crystallized mercury compound, (C t! H 5 S) 2 Hg. 

Cresols, 0?H8O( CeH* < rE 3 Y — There are three cresols, 

elis- 
or hydroxyl derivatives of toluene, of the formula C 6 H 4 < 

They are all found in coal tar, and the tars from pine and beech 
wood. When mixed together, it is difficult to separate them. 
To obtain them in pure condition, it is therefore besl to make 
them from the free toluidines, or from the three sulphonic acids 
of toluene. 

Note fob Student, — Give the equations representing the reactions 
involved in passing from the three toluidines to the cresols, and from the 
three toluene-sulphonio acids to the oresols. 

The cresols resemble phenol very closely. 

Creosote is a mixture of chemical compounds contained in 

wood tar. It contains the cresols. Coal-tar creosote consists 

largely oV phenol. 



304 DERIVATIVES OF THE BENZENE SERIES. 



rCH.3 
Thymol, propyl-meta-cresol, CioHmOI CeH 3 ■! OH (»0 

This phenol is contained in oil of thyme, together with cy- 
mene, and is made artificially from nitro-cuminic aldehyde, 

rCHO 

C 6 H 3 •] N0 2 («0 . When this is reduced it gives an amino deriva- 

l CzH. 7ip) , CH 3 

tive of cymene, C 6 H 3 ■! NH 2 , which can be converted into thymol 

ic 3 H 7 
through the diazo compound. It forms large monoclinic crys- 
tals, which melt at 50°. It has a pleasant odor, like that of 
the oil of thyme. Treated with phosphorus pentoxide, it 
yields meta-cresol and propylene, C 3 H 6 ; while, when treated 
with phosphorus pentasulphide, it yields cymene. These two 
reactions indicate that the groups contained in thymol bear to 
each other the relations indicated by the formula given above. 
It is one of the two theoretically possible hydroxyl derivatives 
of cymene. The other one, carvacrol, has the hydroxyl in the 
ortho position relatively to methyl. It has been made from 
the corresponding cymene-sulphonic acid ; is found in nature 
in the ethereal oil of Origanum hirtum ; and can be made from 
carvol, or the oil of caraway, by heating it with glacial phos- 
phoric acid or with caustic potash. 

Di-acid Phexols. 

The three theoretically possible di-hydroxyl benzenes, 

OH 
C 6 H 4 < are all well known. 
OH 

1 Formulas of this kind serve very well to indicate the relations of the groups and 
atoms contained in benzene derivatives. This one, for example, indicates that the 
hydroxyl is in the meta position (in) to methyl ; while the propyl is in the para 
position to methyl (p). For di-substitution products, such formulas may also 

OH 

be used. Thus, the three toluidines may be represented bv C 6 H 4 <^ 3 

C fi H 4 <? 0il3 , and C 6 H 4 <^ otl3 . 
6 4< NH 2 («0 6 4 ^NH 2 (p) 



DI-ACID PHENOLS. 305 

Pyrocatechol, \ ^ ( OH \ 

Ortho-di-hydroxy-benzene, / CcHeC^CeH* < O H( 0) )' 

This substance is a frequent product of the dry distillation of 

natural substances, — as of catechu, morintannic acid, etc., — 

and of the melting of resins with caustic potash. It can be 

made by fusing ortho-chlor-phenol or ortho-phenol-sulphonic 

acid with caustic potash. It forms crystals, which melt at 

104°. It is easily soluble in water, alcohol, and ether. 

The dilute solution in water gives with ferric chloride a 
dark-green color, which becomes violet on the addition of a 
little of a very dilute solution of sodium carbonate. 

It reduces silver nitrate in solution in cold water. It is 
used in photography. 

Guaiacol, monomethyl pyrocatechol, Cr.Hi < OCHs. 

OH(o) 

This substance was first found in guaiac resin. Hence its 
name. It is formed in considerable quantity in the distilla- 
tion of wood, especially beech-wood. It is made syntheti- 
cally by introducing methyl into pyrocatechol. Guaiacol is a 
liquid that solidifies at 28.5° and boils at 205°. The carbon- 
ate, CO(OC 6 H 4 . OCH 3 ) 2 , has been recommended as a remedy in 
tuberculosis. 

Veratrol, dimethyl pyrocatechol, CeH* < OCH \ j s formed 

OCH; 

by treating the potassium salt of pyrocatechol with methyl 

,CO,II 

iodide and by distilling veratric acid, (\-,\\- J OCH 8j with lime. 

LOCHa 

Resorcinol, IchcW P TT OH ^ 

Meta-di-hydroxy-benzene, 1 UeMeU^-OeHi < QH 

Resorcinol is formed by the melting of a number of resins with 
caustic potash, as oi' galbanum, sagapenum, asafoetida, etc. 
It is made, also, by melting meta-iodo-phenol or meta-benzene- 

disulphonic acid with caustic potash. 

It crystallizes from water, usually in thick rhombic prisms. 
Melting-point, 118°. 



306 DEEIVATIYES OF THE BENZENE SERIES. 

With, ferric chloride, the water solution gives a dark purple 
color. Heated for a few minutes with phthalic acid in a test- 
tube, a yellowish-red mass is formed. When this is added 
to dilute caustic soda, a wonderfully fluorescent solution is 
obtained. The explanation of this reaction will be given 
under the head of Tri-phenyl-methane, when the phthaleins 
will be described. 

Resorcinol is used largely in the manufacture of certain dyes, 
and is therefore manufactured on the large scale. 

Heated with sodium nitrite resorcinol gives a deep-blue dye. 
This is soluble in water and the solution is turned red by 
acids. It is called lacmoid and is used as an indicator. 

Tri-nitro-resorcinol, \ n ^ („„( (N0 2 ) 3 

Styphnic acid, } CeHsNaOs (^H j (OH)j 

This compound is formed by the action of nitric acid on re- 
sorcinol, and on those resins which give resorcinol when treated 
with caustic potash. It closely resembles picric acid. Heated 
with bromine and acetic acid, it yields the substance known 
as bromjricrin, which has the formula C(N0 2 )Br 3 . 

Hydroquinol, IrnnfrTT/ 011 ^ 

Para-di-hydroxy-benzene, 1 u<3±l6U2 ^ 6±l4 < OH(*» J ' 
Hydroquinol is formed by the dry distillation of quinic acid, 
by reduction of quinone (which see), by means of sulphur 
dioxide, by fusing para-iodo-phenol with caustic potash, etc. 

It is a crystallized substance which melts at 169°; easily 
soluble in alcohol, ether, and hot water. 

. Oxidizing agents, such as ferric chloride, chlorine, etc., convert 
it into quinone. It is used in photography as a " developer." 



It would lead too far to discuss here the reactions which 
have been made use of for the purpose of determining to which 
series each of the three di-hydroxy-benzenes belongs. The 
principle involved, however, is simple. Either these substances 
must be converted, directly or indirectly, into others, in regard 



ORCINOL, DI-HYDROXY-TOLTJENE. 307 

to the relation of whose groups we have evidence ; or sub- 
stances, the relation of whose groups is known, must be con- 
verted into the di-hydroxy-benzenes. The reactions made use 
of for effecting the conversions are mainly those which have 
already been studied ; viz., the formation of amino compounds 
from nitro compounds by reduction ; the formation of diazo com- 
pounds from amino compounds ; the formation of (1) hydroxyl 
derivatives, (2) chlorine, bromine, or iodine derivatives, from 
the diazo compounds ; and the formation of hydroxyl deriva- 
tives from sulphonic acids. 

Kdroxy-toluene, } °< H8 °* | °^ f °|»> 



OH(»0 J 

There are two dye-stuffs, known as archil and litmus, which 
are made from different lichens by exposing them in powdered 
condition in ammoniacal solution to the action of air. They 
are treated with decomposing urine, from which the ammonia 
is obtained. Archil contains a substance called orcein, which 
can be made from orcinol by treating it with ammonia. Or- 
cinol is contained in several lichens. It is formed, also, by 
melting aloes with caustic potash, and by melting 1, 3, 5-chlor- 
toluene-sulphonic acid with caustic potash. The last reaction 
shows that orcinol is a di-hydroxy-toluene. 

Orcinol crystallizes in large, colorless, monoclinic prisms. 
Turns red in the air. Ferric chloride turns the aqueous so- 
lution deep violet. 

Treated with ammonia in moist air, it is converted into 
orcein, (\> S II. M N.>0 7 , a substance which dissolves in alkalies. 
forming beautiful red solutions. 

Orcinol is manufactured on the large scale, and then eon- 
verted into orcein, which is used as a dye. 

Litmus is obtained from theliohens RocceKaand Lecanora by 
treating them with ammonia ami potassium carbonate. Com- 
mercial litmus is made by mixing the concentrated solution 
of the potassium salt with chalk or gypsum, 



C 6 H 3 1 CI + ^ nTT = C 6 H 3 ) OH + KC1 + K 2 S0 3 . 



308 DERIVATIVES OF THE BENZENE SERIES. 

Tri-acid Phenols. 

Pyrogallol, pyrogallic acid.l 

Tn-hydroxy-benzene, J J 

Pyrogallic acid is formed by dry distillation of gallic acid, the 
reaction being analogous to that by which benzene is produced 
by distillation of benzoic acid : — 

C 6 H 5 . C0 2 H = C 6 H 6 + C0 2 ; 

Benzoic acid. Benzene. 

C 6 H 2 { (OH), = c 6 H 3 (OH) 3 + C0 2 . 

I OUo-tl Pyrogallol. 

Gallic acid. 

It is formed also when one of the chlor-phenol-sulphonic acids 
is fused with caustic potash : — 

OH KQH ( OH 

S0 3 K K ° H (OH 

Potassium chlor-phenol- Pyrogallol. 

sulphonate. 

It crystallizes in laminae or needles ; melts at 132-133° ; is 
easily soluble in water, ether, and alcohol. In alkaline solution 
it absorbs oxygen rapidly and becomes brown. On account of 
this power to absorb oxygen it is used in gas analysis. It is 
poisonous. With a solution containing a ferrous and a ferric 
salt it gives a blue color. 

Most of the j)henols give color reactions with ferric chloride, 
and most of them change color in the air. These changes in 
color are undoubtedly due to the action of oxygen. Towards 
oxidizing agents they are all unstable, most of them breaking 
down readily and yielding as the chief product of oxidation, 
carbon dioxide. In general, the larger the number of hydroxyl 
groups contained in a phenol, the less stable it is. We shall 
see that these same statements hold good for the hydroxy- 
acids of the benzene group, of which gallic acid and salicylic 
acid are examples. 



ALCOHOLS. 309 



Phloroglucinol, CeHsCOH)? 



ro 



This phenol 



CeHs \ OH (3) 
I OH (5) 

was first obtained from phloretin, which is one of the products 
of decomposition of a glucoside (see glucosides), phloridzin. 
It can be obtained also from other glucosides, and from several 
resins. Orcinol gives it when fused with potassium hydroxide, 
as does 1, 3, 5-benzene-trisulphonic acid. 

In some of its reactions phloroglucinol acts like a trihydroxy- 
benzene, in others it acts as if it contained three carbonyl 
groups, CO. In the present state of our knowledge we can 
only conclude that in contact with some reagents it actually is 
trihydroxybenzene, while in contact with others it is triketo- 
hexamethylene. The two conditions are represented by the 
formulas : — 

C CH 2 



V 



HO . C /\ C . OE 
HC\^CH 




OH 
Trihydroxybenzene. Triketohexamethylene. 

Many cases of this kind are known. The name tautomerism 
is given to this phenomenon. A substance that acts thus, as 
if it had two different structures, is said to appear in two tauto- 
meric forms or to exhibit the phenomenon of tautomerism. 
It will be seen that in order that one form of phloroglucinol 
may be changed to the other a change in the position of three 
hydrogen atoms is necessary. Much attention is being given 
to phenomena of this kind at present. 

Alcohols ov the BENZENE SERIES. 

The phenols are those hydroxy] derivatives o( the benzene 
hydrocarbons, which contain the hydroxy] in the place of one 
or more of the six benzene hydrogens. But just as there are 



310 DERIVATIVES OF THE BENZENE SERIES. 

two classes of halogen substitution-products of toluene, in one 
of which the substitution has taken place in the benzene 
residue, and in the other in the marsh-gas residue, as indicated 
in the two formulas, — 

C 6 H 4 C1 . CH 3 and C 6 H 5 . CH 2 C1, 

so, also, there are two classes of hydroxyl derivatives : (1) the 
phenols, and (2) those in which the hydroxyl is in the marsh- 
gas residue. The simplest example of the second class corre- 
sponds to the formula, C 6 H 5 . CH 2 . OH. It is isomeric with the 
cresols, C 6 H 4 . OH . CH 3 , and has entirely different properties. 
While the cresols are the true homologues of phenol, the new 
substance is methyl alcohol in which one of the hydrogens 
of the methyl has been replaced by phenyl, C 6 H 5 . It may 



be represented by the formula, C j „ , when its analogy to 
r CH 3 L OH 

IT 

ethyl alcohol, CM , is at once apparent. 





Benzyl alcohol, 7 H 8 O(= C 6 H 5 .CH 2 OH).— Benzyl alcohol 
or phenyl carbinol is found in nature in the balsams of Peru 
and Tolu, and in storax. In these substances it is, for the 
most part, in combination with benzoic or cinnamic acid. It is 
made by treating the oil of bitter almonds, which is the corre- 
sponding aldehyde, with nascent hydrogen : — 

Qft.CHO + H 2 = C 6 H 5 .CH 2 .OH. 

Oil of bitter almonds. Benzyl alcohol. 

It is also made by replacing the chlorine in benzyl chloride, 
C 6 H 5 .CH 2 C1, by hydroxyl, just as methyl alcohol is made from 
methyl chloride by a similar replacement. In the case of 
benzyl chloride this can be effected even by boiling for a long 
time with water : — 

C 6 H 3 .CH 2 C1 + H 2 = C 6 H 5 .CH 2 OH -j- HC1. 



BENZYL ALCOHOL. 311 

Benzyl alcohol is a colorless liquid with a pleasant odor. It 
boils at 206.5°. It dissolves with difficulty in water, and is 
soluble in alcohol and ether. 

Note for Student. — Notice the great difference between the boiling- 
point of methyl alcohol and that of phenyl-methyl alcohol. 

Oxidizing agents convert the alcohol, first, into the oil of 
bitter almonds or benzoic aldehyde, and finally into benzoic 
acid. The relations between the three substances are like 
those between any primary alcohol and the corresponding alde- 
hyde and acid, as shown by the formulas : — 

C 6 H 5 .CH 2 OH; or C 6 H 5 .CHO; or C 6 H 5 .C0 2 H. 

Benzyl alcohol. Benzoic aldehyde. Benzoic acid. 

Hydriodic acid converts benzyl alcohol into toluene : — 
C 6 H 5 .CH 2 OH + 2 HI = C 6 H 5 .CH S -f- H 2 + 21. 

Benzyl alcohol conducts itself, in most respects, like the 
primary alcohols of the methyl alcohol series. A large number 
of its derivatives have been made and studied. Among them 
are ethereal salts, of which benzyl acetate, CH 3 .CO.OC 7 H 7 , and 
benzyl nitrate, N0 2 .OC 7 H 7 , may serve as examples; ethers, of 
which the methyl ether, C 6 H 5 .CH 2 .O.CH 8 , and the phenyl ether, 
C 6 H 5 .CH 2 .OC G H 5 , are good examples ; and substitution-products, 
of which chlor-benzyl alcohol, C 6 H 4 C1 .CH 2 OH, and nitro-benzyl 
alcohol, C c II 4 (N0 2 ).CII 2 OH, are examples. 

These substitution-products are not made by direct treatment 
of the alcohol with the substituting agents, but by starting with 
the corresponding substituted toluene. Thus, chlor-benzyl 
alcohol is made from chior- toluene, C \ ; 1 1 t C 1 .(11,, by first con- 
verting this into chlor-benzyl chloride, (\;11,C1.CICCC and then 
replacing the chlorine oi' the group CI LCI by hydroxyl. By 
oxidation the substituted benzyl alcohols yield the correspond- 
ing substituted benzoic acids : — 

C 6 H,C1.CH 2 0H + O, - C„lI t CCOO : IT + ICO. 

Chlor-benxoio mM. 

C 6 H 4 (N0 2 ).C1U)U + O, - C (; ll^N(V)CO,ll + ICO. 

Nilio-bon.oie acid. 



312 ALDEHYDES OF THE BENZENE SERIES. 

Very few of the alcohols analogous to benzyl alcohol have 
been prepared. Plainly, the homologues may be of two kinds : 

1. Those which are phenyl derivatives of the alcohols of the 
metlryl alcohol series. Of this class, phenyl-ethyl alcohol, 
C 6 H 5 .CH 2 .CH 2 OH, the isomeric substance C 6 H 5 .CH. OH. CH 3 , 
and phenyl-propyl alcohol, C 6 H 5 .CH 2 .CH 2 .CH 2 OH, are ex- 
amples. Phenyl-propyl alcohol is of special interest on 
account of its connection with cinnamic acid (which see) , 
which has come into prominence since it has been shown to be 
closely related to the interesting substances of the indigo group. 
It occurs in storax in the form of an ethereal salt, which will 
be spoken of more fully under the head of Cinnamic Acid. 

2. Those which are derivatives of xylene, mesitylene, etc., 
in the same sense that benzyl alcohol is a derivative of toluene. 
The following belong to this class : — 

Tolyl-carbinol .... C 6 H 4 < CH3 , 
J CH 2 OH' 

and Cuminyl alcohol . . . . C 6 H 4 < CH2 ° H , 

C 3 H 7 (p) 

which is made from cuminol, an aldehyde found in the oil of 
caraway. 

Aldehydes of the Benzene Series. 

The aldehydes of this group are closely related to the alco- 
hols just considered. The simplest one is the oil of bitter 
almonds, or benzoic aldehyde, C 7 H 6 0. 



Oil of bitter almonds, , C7HeO(06H5 . CHO) . _ TMs sub . 

Benzoic aldehyde, > 
stance occurs in combination in amygdalin, which is found in 
bitter almonds, laurel leaves, cherry kernels, etc. Amygdalin 
belongs to the class of bodies known as glucosides, which break 
up into a glucose and other substances. Amygdalin itself, 
under the influence of emulsin, which occurs with it in the 



BENZOIC ALDEHYDE. 313 

plants, breaks up into benzoic aldehyde, hydrocyanic acid, and 
dextrose : — 

CaoH^NOu + 2 H 2 = C 7 H 6 + CNH + 2 C 6 H 12 G . 

Amygdalin. Benzoic aldehyde. Glucose. 

Benzoic aldehyde can be made : 

1. By oxidizing benzyl alcohol : — 

C 6 H 5 . CH 2 OH + = C 6 H 5 . CHO + H 2 0. 

2. By distilling a mixture of calcium benzoate and calcium 
formate : — 

C 6 H 5 . COJOMj = CH0 co 

H.ICOOM! 



3. By treating benzoyl chloride, the chloride of benzoic acid, 
with nascent hydrogen : — 

C 6 H 5 . COC1 + H 2 = C 6 H 5 . CHO + HC1. 

4. By treating benzal chloride with water and milk of lime 
under pressure : — 

C 6 H 5 . CHC1 2 + H 2 = C 6 H fi . CHO + 2 HC1. 

Note for Student. — Refer to the general methods for the prepara- 
tion of aldehydes. Which of the above reactions are used for the 
preparation of aldehydes in general ? Which of the reactions throw light 
upon the nature of aldehydes, and their relation to alcohols '.' 

Benzoic aldehyde is prepared either from bitter almonds, 
which yield about 1.5 to 2 per cenl ; or from benzal chloride. 
On the large scale it is prepared by treating benzyl chloride 
with lead nitrate. The change is that represented in reaction 
■I above. 

Benzoic aldehyde is a liquid having a pleasanl characteristic 
odor. It, boils at 170°; is difficultly soluble in water; is not 
poisonous. 

It unites with oxygen to form benzoic acid; with hydrogen 
to form benzyl alcohol; with hydrogen sulphide, ammonia, 
nnnuoniijni sulphide, alcohols, acids, anhydrides, ami ketones, 



314 



DERIVATIVES OF THE BEXZEXE SERIES. 



In short, its powers of combination with other substances are 
almost unlimited. Hence, a very large number of derivatives 
are known. 

Cuminic aldehyde, cuminol, C10H12O1 CeH4< zri¥ | 

V CsHiip)]' 

This aldehyde occurs in oil of caraway, from which it is made. 
It is a liquid with the odor of the oil of caraway. Its reactions 
are like those of benzoic aldehyde. 

Benzaldoximes, CeHs • CH=N • OH. — Hydroxy lamine re- 
acts with benzoic aldehyde as it generally reacts with aldehydes, 
forming an oxime : — 

C 6 H 5 . CHO + HoNOH = C 6 H 5 . CH=N . OH + H 2 0. 

This appears first as an oil, but when purified it forms long, 
lustrous prisms, melting at 34°. 

When hydrochloric acid gas is conducted into an ether solu- 
tion of the above oxime, a hydrochloride is precipitated, and 
when this is treated with sodium carbonate, a new oxime, 
isomeric with the above, is obtained. This crystallizes from 
ether in thin, lustrous needles, and melts, when rapidly heated, 
at 128-130°. By continued heating, however, it is converted 
into the oxime, melting at 34°. 

These two oximes are regarded as stereoisomeric. In terms 
of the conceptions of stereochemistry they should be represented 
by the formulas : — 

n H c -C-H and CJ3 K -C-H 



HO-N 



X-OH 



or 




and 




OH 



MONOBASIC ACIDS 315 

[For an explanation of the significance of these formulas, 
especially as far as the nitrogen atom is concerned, see p. 290.] 

The one with the hydrogen atom and the hydroxyl on oppo- 
site sides is called benzayitialdoxime ; the one with the hydrogen 
atom and the hydroxyl on the same side is called benzsynal- 
doxime. The one that melts at 128-130° easily loses water and 
forms phenyl cyanide or benzonitril, C 6 H 5 — CN. The other 
does not. It is believed that the one that loses water and 
yields the nitril is the synoxime. According to this the stable 
form, the one most easily obtained, is the antioxime. Phenom- 
ena of this kind have been extensively studied and the ideas 
here set forth rest upon a broad foundation of experimental 
evidence. 

Acids of the Benzene Series. 

The simplest of these acids is benzoic acid, which bears to 
benzene the same relation that acetic acid bears to marsh-gas. 
It is the carboxyl derivative of benzene. The homologous 
acids are derivatives of the homologous hydrocarbons. There 
are mono-basic, di-basic, tri-basic, and even hexa-basic acids, 
but the number actually known is small. 

Monobasic Acids, ( J n 1 1 o n _ 8 0._,. 

Benzoic acid, CtHgCKCH. OO2H). — Benzoic acid occurs 
in gum benzoin, in the balsams of Pern and Tolu, and in 
combination with amino-acetic acid or glycine in the urine of 
herbivorous animals. It can be made in many ways, the most 
important of which are given below: — 

lo By oxidation oi' benzyl alcohol or any alcohol which is a 
phenyl derivative of an alcohol oi' the methyl alcohol series. 

The common condition in all these alcohols is the presence o( 

the difficultly oxidizable residue, C e H 5 , in combination with an 

easily oxidizable residue oi' an alcohol o( the marsh-gas series : — 

C (; Il,.CH,011 gives CeHj.COaH ; 

o,ii,.cn,.rii,,oii - r,n,. com : 

(\H„.riI,.01l,.ril,OH « (\H-.- CO,H, ete. 



316 DERIVATIVES OF THE BENZENE SERIES. 

2. By oxidation of benzoic aldehyde, and the aldehydes of 
the other alcohols referred to in the preceding paragraph. 

3. By oxidation of all benzene hydrocarbons which contain 
but one residue of the marsh-gas series. Attention has already 
been called to this fact (see p. 265). 

4. By treating cyan-benzene (phenyl cyanide, benzo-nitrile) 
with sulphuric acid (see Exp. 65, p. 294) : — 

C 6 H 5 CN + 2 H 2 - C 6 H 5 . C0 2 H + NH 3 . 

5. By treating benzene with carbonyl chloride in the presence 
of aluminium chloride : — 

C 6 H 6 + COCl 2 = C 6 H 5 .C0C1 + HC1; 

C 6 H 5 .C0C1 + H 2 = C 6 H 5 .C0 2 H + HC1. 

A reaction similar to this is of extensive application in the 
preparation of some hydrocarbons. It will be treated of more 
fully under the head of Tri-phenyl-methane. 

6. By treating benzene with carbon dioxide in the presence 
of aluminium chloride : — 

C 6 H 6 + C0 2 = C 6 H 5 .C0 2 H. 

This and the preceding methods are of special interest from the 
scientific point of view, for the reason that they clearly show 
the relation between benzoic acid, on the one hand, and ben- 
zene and carbonic acid, on the other. 

Note for Student. — Which of the methods above given are of 
general application for the preparation of the acids of carbon? 

Benzoic acid is prepared on the large scale : (1) from gum 
benzoin b} r sublimation ; (2) from the urine of horses and 
cows by treating the hippuric acid with hydrochloric acid ; 
(3) from toluene, best, by converting it into benzyl chloride, 
and oxidizing this with dilute nitric acid. 

Experiment 69. If the material is obtainable, evaporate a quantity 
of the urine of horses or cows to about one-half or one-third its vol- 



BENZOIC ACID. 317 

ume. Add hydrochloric acid. On cooling, hippuric acid will be 
deposited. Recrystallize this several times from dilute nitric acid. 
Boil the hippuric acid for about a quarter of an hour with ordinary 
concentrated hydrochloric acid. By this means the hippuric acid is 
decomposed, yielding glycine (amido-acetic acid) and benzoic acid : — 

C 9 H 9 N0 3 + H 2 = C 7 H 6 2 + CH 2 < ^ 2 

Hippuric acid. Benzoic acid. 2 

Glycine. 

Benzoic acid forms lustrous laminae or needles, which melt 
at 121°. 

Experiment 70. Determine the melting-point of the benzoic 
acid which you have made from hippuric acid. If it is not as 
stated above, recrystallize from water until the melting-point is not 
changed by further crystallization. Those specimens which are 
least pure can be purified by recrystallizing them from dilute nitric 
acid. 

The acid is comparatively easily soluble in hot water, but 
difficultly soluble in cold water. It is volatile with water 
vapor. 

Experiment 71. Put some in a one-litre flask, with about 700 cc 
to 800 cc water. Connect with a condenser, and boil down to about 
200 cc . Neutralize the distillate with ammonia, and evaporate down 
to a small volume. Acidify, when benzoic acid will be thrown 
down. 

Its vapor acts upon the mucous membrane of the respira- 
tory passages, and causes coughing. 
It sublimes very easiby. 

Experiment 72. Put sonic dry benzoic acid in a small, dry crys- 
tallizing dish, and put the dish in a sand-bath. Over the mouth ol" 
the dish put a, paper cone made from filter-paper, arranged as shown 
in Fig. 1(5. Heat, with a small tlame. The benzoic acid will be depos- 
ited on the paper in beautiful lustrous needles. 

Or another form o( apparatus, which is useful for subliming small 
quantifies of substance, consists, essentially, o( two watch-glasses 
which arc of exactly the same size. The edges of the glasses are 
ground to secure a good joint, when they are brought together. In 



318 



DERIVATIVES OF THE BENZENE SERIES. 



using this apparatus, put the substance to be sublimed in one of the 
glasses ; stretch a round piece of filter-paper over it, and then place 
the other glass upon it. Clamp the glasses together by means of a 
thin brass clamp. Now put the glasses on a sand-bath, and warm 




Fig. 16. 

gently, when the substance will slowly pass through the paper and 
appear in crystals in the upper watch-glass. It is well to keep a small 
pad of moist filter-paper on the upper glass during the operation. 

When heated with lime, benzoic acid breaks up into benzene 
and carbon dioxide (see Exp. 55) : — 

C 7 H 6 2 = C 6 H 6 + C0 2 . 

With sodium amalgam, it yields benzyl alcohol and other reduc- 
tion-products. With hydriodic acid, it yields toluene, and then 
hydrogen addition- products of toluene. 

A great man} T derivatives of benzoic acid are known. 



BENZOYL CYANIDE. 319 

Nearly all its salts are soluble in water. 
The ethereal salts can be made by any of the general 
methods already described. 

Note for Student. — What are the general methods for the prepa- 
ration of ethe'real salts ? 

Experiment 73. Dissolve 40s benzoic acid in 150 cc absolute alcohol. 
Pass dry hydrochloric acid gas into the solution, keeping the latter cool 
by surrounding it with water. When the solution is saturated with 
hydrochloric acid, connect the flask with an inverted condenser, and 
warm gently on a water-hath for half an hour. Now add three or four 
volumes of water, when ethyl benzoate will separate as an oil. Wash 
with water and a little sodium carbonate ; and, finally, dry. 

Benzoyl chloride, CcHs . COC1, and bromide, C 6 H 5 . COBr, 
are made from benzoic acid in the same way that acetyl chlo- 
ride is made from acetic acid. They are more stable than the 
corresponding compounds of the fatty acids, but in general 
undergo the same kinds of change. 

Benzoyl chloride acts upon hydroxy! compounds in the same 
general way that acetyl chloride does, and forms benzoyl com- 
pounds : — 

C 6 H 5 . OH + C 6 H 5 . COC1 = C 6 H C . CO . . B H, + HC1. 

These benzoyl compounds are, as will be seen, esters oi' ben- 
zoic acid. 

The reaction between hydroxy! compounds and benzoyl 
chloride is much aided by the addition of caustic potash. 

Benzoyl cyanide, CeH5.OO.ON, is made by distilling 
mercuric cyanide and benzoyl chloride: 

2C e H 8 .COC] + Hg(CN) 2 = 2C 6 H 5 .COCT + ffgCl* 

The cyanogen can be converted into carboxyl, and thus an acid 
of bhe formula C 6 H 8 .CO.C0 2 H obtained. This is known as 
benzoyl-formic acid. It is of interest, for the reason that one 
of its derivatives is also a derivative of indigo (see [satine). 



320 DERIVATIVES OF THE BENZENE SERIES. 

Substitution-Products of Benzoic Acid. 

Benzoic acid readily yields substitution-products when treated 
with the halogens, and with nitric and sulphuric acids. The 
products obtained by direct substitution belong mostly to 
the nieta series. Thus, when chlorine acts upon benzoic acid, 
the main product is meta-chlor-benzoic acid; nitric acid gives 
mainly metornitro-benzoic acid; and sulphuric acid gives mainly 
meta-sulpho-benzoic acid. 

Note for Student. — Compare this with the result of the direct 
action of the same reagents on toluene. What are the first products 
of the action of nitric and sulphuric acids on toluene ? 

Substituted benzoic acids can be made, also, by oxidizing the 
corresponding substituted toluenes. Thus, chlor-toluene gives 
chlor-benzoic acid ; nitro-toluene gives nitro-benzoic acid, etc. : — 

C 6 H 4 C1 . CH 3 gives C 6 H 4 C1 . C0 2 H ; 
C 6 H 4 (N0 2 )CH 3 " C 6 H 4 (N0 2 )C0 2 H. 

The three nitro-benzoic acids and the corresponding amino- 
benzoic acids may serve as examples of the mono-substitution 
products. 

Ortho-nitro-benzoic acid, C7H5NO4 f CeHi < ^q H } — 

Ortho-nitro-benzoic acid is formed, together with a large quan- 
tity of the meta acid and some of the para acid, by treating 
benzoic acid with nitric acid, by oxidizing ortho-nitro-toluene 
with potassium permanganate, and by oxidizing ortho-nitro- 
cinnamic acid. It crystallizes in needles, melts at 147°, and 
has an intensely sweet taste. 

Meta-nitro-benzoic acid, CeH4 < J™ , is the chief prod- 

-D*J U2(m) 

net of the action of nitric acid on benzoic acid. It crystallizes 
in laminse, or plates, and melts at 140° to 141°. 

Para-nitro-benzoic acid, CgH4<9J? , is prepared best 

NO2Q,) 

by oxidizing para-nitro-toluene. It crystallizes in laminae, 



ANTHRANILIC ACID. 321 

melts at 238°, and is much less easily soluble in water than 
the ortho and meta acids. 

The determination of the series to which these three acids 
belong is effected by transforming them into the amino-acids ; 
and these, through the diazo compounds, into the corresponding 

AIT 

hydroxy-acids of the formula C 6 H 4 < CQ „• 

Note for Student. — Give the equations representing the action 
involved in passing from toluene to ortho-hydroxy-benzoic acid (sali- 
cylic acid) by the method above referred to. 

In a similar way, lines of connection can be established 
between the three hydroxy-acids and the chlor-, brom-, and 
iodo-benzoic acids. 

Note for Student. — What are the reactions ? 

The three hydroxy-acids, on the other hand, have been made 
by methods that connect them directly with the three dibasic 

pA TT 

acids of benzene, C 6 H 4 < nn 2 TJ j which, in turn, have been made 
from the three xylenes. 

Ortho-amino-benzoic acid, \ c-H-NO Yc H < ^O-H 
Anthranilic acid, -* ' \ NHaw 

— This acid is made by reducing ortho-nitro-benzoic acid with 
tin and hydrochloric acid, and by boiling indigo with caustic 
potash. It has already been stated that indigo yields aniline. 
Now, as ortho-amino-benzoic acid is also obtained, and this 
breaks up easily into aniline and carbon dioxide. 

C,H 4 <^ = C,H„.NH, + CO a 

it seems probable that the aniline is a secondary product. 

Like other amino acids, anthranilic acid is probably an inner 
salt and should, accordingly, be represented by the formula 

^ 8 *** < -kttt 9 > • When it is diazotized it yields an inner dia- 
IS 11;; »r\ 

zonium salt of the formula (\,U.t < N ~>« 

III 

N 



322 DERIVATIVES OF THE BENZENE SERIES. 

Isatme,C 8 H 5 N02/'C6H4<2. >C.OHorC6H4<S-?T>CO\ 

V N NH J 

— Isatine is obtained by the oxidation of indigo, and from 
ortho-amino-benzoic acid as follows : — 

The amino-acid is converted into the chloride, the chloride 
into the cyanide, and this into the corresponding carboxyl 
derivative, which is the ortho-ammo derivative of benzoyl- 
formic acid. The ortho-amino-benzoyl-formic acid thus ob- 
tained loses water, and is converted into isatine. The changes 
are represented by these equations : — 

« ca 4h!S +pci = = c ^4hV hc1+P0C1 ' ; 

Ortho-amino-benzoic acid. Ortho-amino-benzoyl 

chloride. 

Ortho-amino-benzoyl 
cyanide. 

Ortho-amino-benzoyl- 
formic acid. 

(4) C 6 H t < Jg ??° H = 6 H 4 < C° >C . OH + H 2 0, 

orC 6 H 4 <CO >co . 

Isatine. 

The formula given for isatine represents it as an anhy- 
dride of ortho-amino-benzoyl-formic acid. The formation of 
anhydrides of aromatic acids is a characteristic of ortho 
compounds. Neither the meta nor para acids give up 
water. We shall find that this fact is illustrated in the case 
of the dibasic acids, the only one that yields an anhydride 

POOH 

being ortho-phthalic acid, C 6 H 4 < nnOTT ^ v wn i° n gives phthalic 

CO bUUM(O) 

anhydride, C 6 H 4 < ro > 0. This ready formation of anhydrides 

from ortho compounds, taken together with the fact that the 
meta and para compounds do not yield anhydrides, has been 



HIPPURIC ACID. 323 

regarded as an argument in favor of the view that in the ortho 
compounds the two substituting groups are actually nearer 
together than in the meta and para compounds. 

Isatiue illustrates the phenomenon of tautomerism (see page 
309). Towards some reagents it reacts as though it contained 
hydroxyl ; towards others as though it contained the imino 
group NH, as represented by the two formulas : — 

QP,<^>00 and C 6 H 4 < ^° ^ C . OH. 

The relation of isatine to indigo will be discussed briefly 
under the head of Indigo. 

Meta- and Para-amino-benzoic acids are made from 
the corresponding nitro acids by reduction. 

Hippuric acid, benzoyl-amino-acetic acid, 
CoH 9 N0 5 (= C 6 H 5 . CONH . 0H 2 0O 2 H). 

Hippuric acid, as has already been seen (Exp. 69), occurs in 
the urine of herbivorous animals, as the cow, horse, camel, and 
sheep. Some hippuric acid is found in human urine under 
ordinary circumstances. If benzoic acid is taken with the 
food, it appears as hippuric acid in the urine, while derivatives 
of benzoic acid appear as derivatives of hippuric acid. 

Hippuric acid can be made synthetically from benzoic acid 
and acetic acid : 

1. P>y heating glycine with benzoic acid to L60°: — 



Hippuric add. 

'2. By heating benzamide with chlor-acetic acid: — 

C 6 H 8 .CO.]SrHH4- GJ >CH 6 H 8 .CONH >CH , lh -j 

11 ' uor nor 

Hippuric ftoid. 

3. By heating glycine with benzoyl chloride : — 

CH,<™ + 01.00.0,H 1 CH,. ^"• C0C « H '+HCl 



324 DERIVATIVES OF THE BENZENE SERIES. 

Hippuric acid crystallizes from water in long, rhombic prisms. 

It is decomposed into benzoic acid and glycine by boiling 
with alkalies, and more readily by boiling with dilute acids 
(Exp. 69): — 

CH 2 < ^ H ° 7H5 ° + H 2 = CH 2 < ^ + C 6 H 5 . C0 2 H. 

Note for Student. — What relation does hippuric acid bear to ben- 
zamide ? What is the effect of boiling acid amides with alkalies ? Write 
the equation for the decomposition of benzamide, and compare it with 
that for the decomposition of hippuric acid. 

Toluic acids, CsHsOj. — There are four acids of this formula 
known ; viz., the three carboxyl derivatives of toluene in which 

OH 
the carboxyl enters into the benzene ring, C 6 H 4 < 3 and an 

acid obtained from toluene by replacing a hydrogen of the 
methyl by carboxyl, thus, C 6 H 5 . CH 2 . C0 2 H. Ortho-, metar, 

nil 

and parartoluic acids, C 6 H 4 < 3 , are made by oxidizing the 
corresponding xylenes with nitric acid : — 

C 6 H 4 < CH 3 + 3 Q = CeH4 < C0 2 H + H2() 
U±i 3 0±i 3 

They, as well as their derivatives, of which many are known, 
have been studied carefully. The substituted toluic acids can 
be made either by treating the acids with strong reagents or 
by oxidizing substituted xylenes : — 

C 6 H 3 (N0 2 ) < °?» + 3 = C 6 H 3 (N0 2 ) < ^ H + H 2 0. 

U±l 3 ^ri3 

Mtro-xylene. Nitro-toluic acid. 

a-Toluic acid, •» „ ,_ ^ ,_ _ „_ _ _ „ N T 

Phenyl-acetfc acid, } OH.O,(CWI. .CH 2 .OOfl). -Just as 

benzoic acid may be regarded as phenyl-formic acid, so a-toluic 
acid may be regarded as phenyl-acetic acid. It is obtained by re- 
ducing mandelic or phenyl-glycolic acid, C 6 H 5 .CH(OH).C0 2 H, 
which is formed when amygdalin is treated with hydrochloric 
acid. It is prepared from toluene by converting this into 
benzyl chloride, from which the cyanide is majle bv foiling 



MESITYLENIC ACID. 325 

with, potassium cyanide. The cyanide is then treated with an 
alkali, and yields the acid : — 

C 6 H 5 .CH 3 +C1 2 = C 6 H 5 .CH 2 C1 +HC1; 

Boiling toluene. Benzyl chloride. 

C 6 H 5 . CH 2 C1 + KCN = C 6 H 5 . CH 2 CN + KC1 ; 

Benzyl cyanide. 

C 6 H 5 . CH 2 CN + 2 H 2 = C 6 H 5 . CH 2 . C0 2 H + NH 3 . 

a-Toluic acid. 

The acid crystallizes in thin laminae ; and melts at 76.5°. 

Note for Student. — What would you expect a-toluic acid to yield 
when oxidized ? (See p. 265.) What would you expect it to yield 
when distilled with lime ? What would you expect the three toluic 

acids, C 6 H 4 < 3 , to yield by oxidation, and when distilled with lime ? 

COqH 
(See p. 318.) 

Oxindol, C8H 7 N0(CgH4<9.?:>C0, or C 6 H4< C ;?->C.Oh). 

— Oxindol is obtained by reduction of isatine (see p. 322) ; and 
also from ortho-amino-a-toluic acid by loss of water, in the 
same way that isatine is formed from ortho-amino-benzoyl- 
formic acid. When a-toluic acid is treated with nitric acid, the 
para- and ortho-nitro acids are formed. The latter is reduced 
by means of tin and hydrochloric acid, when oxindol is at once 
obtained : — 

CcH4< NET C00H = ° cH4 < NH > °° + " 

Ortho-amino-a-toluic acid. Oxindol. 

Mesitylenic acid, C..HioO,-( = CcHa (<S?g 8 ). — This acid 

has already been referred to as the first product of oxidation 

of mesitylene. It is the only monobasic acid that has been 
obtained from mesitylene; and, according to the accepted 
hypothesis, it is the only one possible. By distillation with 
lime, it yields meta-xylene. Further oxidation converts it 
into uvitic and trimesitic acids (see p, 266). 

Note for Student. — Of what special significance is the formation 
of meta-xylene from mesitylenic acid ? 



326 DERIVATIVES OF THE BENZEXE SERIES. 

Hydro-cinnamic acid, 1 r „ nrPTT rTT rTT rnT j, 
Phenyl-propionic acid, J C ^^°^^ • °H 2 . OH2 . CO2H). 
— Hydro-cinnamic or phenyl-propionic acid is obtained by 
treating cinnainic acid with nascent hydrogen : — 

C 6 H 5 . CH : CH . C0 2 H + H 2 = C 6 H 5 . CH 2 . CH 2 . C0 2 H. 

Cinnamic acid, Hydro-cinnamic acid, 

/3-Phenyl-acrylic acid. /3-Phenyl-propionic acid. 

It is also made by starting with ethyl-benzene, C 6 H 5 . C 2 H 5 , 
and rising the same reactions that are necessary to transform 
toluene into a-toluic acid (see p. 324). It is a product of the 
decay of several animal substances, such as albumin, fibrin, 
brain, etc. It crystallizes from water, in long needles, which 
melt at 47°. It yields benzoic acid when oxidized. 

Ortho-amino-hydro- 1 C6H4 < CH* ■ CH 2 . CO.H _ TMs acid 
cinnamic acid, J NH200 

is prepared from hydro-cinnamic acid in the same way that 
ortho-amino-a-toluic acid is made from a-toluic acid. It is not 
obtained in the free state; but, like the ortho-amino deriva- 
tives of benzoyl-formic and of a-toluic acids, it loses water, and 
forms the anhydride. 

Hydro-carbostyril, C 6 H4 < ^ 4 > CO. — Hydro - carbo- 

styril is made by treating ortho-nitro-hydro-cinnamic acid with 
tin and hydrochloric acid. It is a solid which crystallizes in 
prisms, melting at 160°. It is interesting chiefly for the reason 
that it is closely related to the important compound quinoline 
(which see). When treated with phosphorus pentachloride, 
hydro-carbostyril is converted into di-chlor-quinoline. The 
significance of this reaction will appear later. 

Dibasic Acids, C n H 2n _ 10 O 4 . 
The simplest acids of this group are the three phthalic acids, 
which are the di-carboxyl derivatives of benzene, belonging to 
the ortho, meta, and para series. 

Phthalic acid, }csH 6 o/ = C 6 H 4 <^ 2 ^- Plltlialic 

Ortho-phthahc acid, J V COitiJ 

acid was the first of the three acids of this composition dis- 



PHTHALIC ANHYDRIDE. 327 

covered; and, as it was obtained from naphthalene, it was 
named phthalic acid. It is manufactured on the large scale 
by oxidizing naphthalene by means of sulphuric acid. It can 
further be formed from alizarin and purpurin ; and from ortho- 

pit 
toluic acid, C 6 H 4 < z| * T , by oxidation with potassium per- 

C0 2 H.( ) 
manganate. 

Experiment 74. Mix 40s naphthalene and 80s potassium chlorate, 
and add this mixture gradually to 400s ordinary concentrated hydro- 
chloric acid. Naphthalene tetra-chloride, CioH 8 . CI4, is formed in this 
reaction. Wash with water. Gradually add 400s ordinary concentrated 
nitric acid (sp. gr. 1.45), and boil in a large retort with upright neck. 
When all is dissolved, evaporate the nitric acid ; and, finally, distil the 
residue. Phthalic anhydride passes over. Recrystallize from water. This 
will be used for other experiments. 

Phthalic acid forms rhombic crystals, which melt at 213° or 
lower, according to circumstances, as, when heated, it breaks 
up gradually, even below the melting-point, into water and the 
anhydride which melts at 128°. Distilled with lime, it yields 
benzene ; though, by selecting the right proportions, benzoic 
acid can be obtained : — 

(1) C (i H 4 <^][ = (',il, + -'0O 2 ; 

(2) C li H 4 <^[]=(\..ll.-,.(H\ll+('0 ; . 

Phthalic acid is decomposed by chromic acid, yielding only 
carbon dioxide and water. Hence, ortho-xylene, when treated 
with chromic acid, docs not yield phthalic acid. By boiling 
ortho-xylene with nitric acid, however, it yields ortho-toluic 
acid, C 6 ll 4 < r :; , and this can be oxidized to phthalic acid 

by treatment with potassium permanganate, 

CO 
Phthalic anhydride, C-.H. < z^^ O. is formed by heat- 

ing phthalic acid. It forms long needles, which melt at 128°, 
Heated with phenols, it- forms the compounds known as phthal- 
chis (which see). 



328 DERIVATIVES OF THE BENZENE SERIES. 

Isophthalic acid, \ „ TT ^ C0 2 H . „ , , 

tv/t 4. uii. v -j C 6H 4 < rn " n/ NJ is formed by oxi- 

Meta-phthalic acid, ) O0 2 ±±(m)' •> 

dizing either meta-xylene or meta-toluic acid with chromic 
acid ; by distilling meta-benzene-disulphonic acid with potas- 
sium cyanide, and boiling the resulting dicyanide with an 
alkali. 

Note for Student. — Write the equations representing the action 
involved in passing from meta-benzene-disulphonic acid to isophthalic 
acid. Into which dihydroxy-benzene is this same disulphonic acid 
converted by melting it with caustic potash? 

The acid is formed, further, by treating meta-sulpho-benzoic 
acid with sodium formate : — 

CA< soJ») + H - C0 * Na = *»<$£-> + HNaS0 °- 

Potassium sulpho- Potassium iso- 

benzoate. phthalate. 

This reaction is of importance, for the reason that the same 
sulpho-benzoic acid, which is thus converted into isophthalic 
acid, can also be converted into one of the three hydroxy- 
benzoic acids ; and thus connection is established between 
the latter and isophthalic acid and meta-xylene. 

Isophthalic acid crystallizes in fine needles from water. It 
melts above 300°, and is not converted into an anhydride. 



Terephthalic acid, ) -, -„. . C0 2 H ™ «,, ,. ., 

^ , ,, ,. . , V C 6 H 4 < ~,,-v Vr . — Terephthalic acid 

Para-phthahc acid, / C0 2 Hq>) F 

is formed by oxidation of the oil of turpentine, 1 cymene, para- 

x3 T lene, and para-toluic acid ; by heating a mixture of potassium 

para-sulpho-benzoate and sodium formate : — 

C 6 H 4 < C ° 2K x + H.C0 2 Na = C 6 H 4 < C ° 2K + HNaS0 3 . 

6 4 S0 3 K(P) C0 2 K(P) T 3 

Potassium para- Potassium tere- 

sulpho-benzoate. phthalate. 

1 The prefix tere is derived from the Latin terebinthinus, turpentine. 



PHENOL-ACIDS OF THE BENZENE SERIES. 



329 



Para-sulpho-benzoic acid is converted into one of the three 
hydroxy-benzoic acids by caustic potash. In the para as well 
as the meta series, the lines of connection indicated below have 
been established : — 



C 6 H 4 < 



OH 
CO,H 



C 6 H 4 < 



C0 2 H 
SO,H 



C 6 H 4 < 



C 6 H 4 < 

4\ 



V 
C0 2 H 
COJH 



CH S 
CH, 



\f 



< C 6 H 4 < 



CH 3 
C0 2 H 



pit . 0H < CH - SQ 3 H 
C 6 H 4<OH <— C 6 H 4<s03H 

Terephthalic acid is a solid which is practically insoluble in 
water. It sublimes without melting and, like isophthalic acid, 
yields no anhydride. 

Hexabasic Acid. 

Mellitic acid, 12 H 6 O 12 [= C 6 (CO 2 H) ]. — This acid occurs 
in nature in the form of the aluminium salt, as the mineral 
honey-stone or mellite. The mineral is rare, and is found in 
beds of lignite. Mellitic acid has been made by direct oxida- 
tion of carbon with potassium permanganate, and by oxidation 
of hexa-methyl-benzene, C 6 (CH 8 ) 6 . By ignition with soda-lime 
it is converted into benzene and carbon dioxide : — 

C e (C0 2 H) 6 = 0,11.4- GCOo. 

Phenol-acids, or Htdroxt-acids or the Benzene Series. 
It will be remembered (hat the alcohol acids or hvdroxv- 
acids of the paraffin series form an important class, including 
such compounds as glycolic, lactic, malic, tartaric, and citric 
acids. The peculiarity o\' these compounds is their double 
Character. They are at the same time alcohols and aeids. 
though the aeid properties are more prominent than the aloe- 



330 DERIVATIVES OF THE BENZENE SERIES. 

holic. The hydroxy-acids of the benzene series bear the same 
relations to the benzene hydrocarbons that the hydroxy-acids 
already studied bear to the paraffins. The simplest are those 
which contain one hydroxyl and one carboxyl in benzene, 

having the formula C 6 H 4 < TT . 

CO2H 

MONO-HYDROXY-BENZOIC AdDS, C 7 H 6 3 . 

Salicylic acid, -> ' OH ~ , . ,. 

Ortho-hydroxy-benzoic acid, J C6H4< C0 2 H(^~" foallc ^ llc 

acid is found in the form of an ethereal salt of methyl, in the 
oil of wintergreen, prepared from the blossoms of Gaultheria 
procumbens. It is formed in a number of ways, among which 
the following should be specially mentioned : — 

1. By converting ortho-amino-benzoic acid into the diazo 
compound, and boiling with water (see p. 286). 

Note for Student. — Give the equations representing the reactions. 

2. By melting ortho-sulpho-benzoic acid with caustic potash. 
Note for Student. — Write the equation. 

3. By treating sodium phenolate with carbon dioxide. The 
sodium salt is first saturated with carbon dioxide under press- 
ure in closed vessels. This gives sodium phenyl carbonate, 
C 6 H 5 . . CO . ONa. By heating this to 120-130° under press- 
ure it is converted into sodium salicylate : — 

C 6 H 5 . . CO . ONa = C 6 H 4 < <™ . 

C0 2 Na 

4. By heating phenol with tetra-chlor-m ethane and alcoholic 
potash : — 

C 6 H 5 . OH + CC1 4 + 6 KOH = C 6 H 4 < ^ + 4 KC1 + 4 H 2 0. 

5. By saponifying the methyl salicylate found in oil of 
wintergreen : — 

W < C0 2 CH 3 + K ° H = C A < cSk + CH '° H - 



SALICYLIC ACID. 



331 



Experiment 75. Boil 30 cc to 40 cc oil of wintergreen with moder- 
ately strong caustic potash in a flask connected with an inverted con- 
denser. When it is dissolved, acidify with hydrochloric acid. Filter 
off the salicylic acid which separates, and re crystallize from water. 

Experiment 76. Dissolve 80s sodium hydroxide and 40* phenol in 
130 cc water in a litre flask, arranged as in Fig. 17. If the mixture is 
cool, heat to 50-60°, and remove the flame. Slowly add 60° chloroform, 
shaking the mixture for several minutes after each addition. The mix- 
ture gradually becomes dark colored. An hour or more may be required 




to complete the addition of all the chloroform. When the action is 
over, boil for an hour, and then distil off the excess of chloroform on 
the water-bath. Acidify with dilute hydrochloric acid, when a thick 

reddish brown oil comes down. Distil in steam as in K\p. 07, until the 
distillate no longer appears in milky drops. A light -colored oil con- 
sisting of salicylic aldehyde and phenol settles in the receiver. Decant 
the Supernatant water. Extrad With ether, and concentrate the extract 
by evaporation in a water-bath. To the concentrated extract add a satu- 
rated solution of mono-sodium sulphite (freshly prepared by dissolving 



332 DERIVATIVES OF THE BENZEKE SERIES. 

40& sodium sulphite in 75 cc hot water, cooling the solution, and satu- 
rating with sulphur dioxide) . Shake the mixture 8 or 10 times, 2 or 
3 minutes at a time, for half an hour; then allow it to stand for sev- 
eral hours. The aldehyde unites with the sulphite, forming small, 
glistening, white crystals, while the phenol remains in solution in the 
ether. Eilter with the aid of a pump, and wash the crystals with alcohol. 
Then treat the crystals on the water-bath with hydrochloric acid, when 
salicylic aldehyde is thrown down. Extract completely with ether, sepa- 
rate the two solutions, and evaporate the ether. 

In an iron or silver dish, melt 25s caustic potash ; remove the lamp ; 
and add the salicylic aldehyde drop by drop, stirring constantly. The 
potassium salt of salicylic acid is thus formed. After the mass is 
cooled, dissolve in water, and precipitate the salicylic acid with dilute 
hydrochloric acid. Eilter, wash with cold water s and purify by recrys- 
tallizing from water. 

The action of chloroform on phenol in the presence of caustic 
soda is analogous to that of tetra-chlor-methane. It will be 
understood with the aid of the following equations : — 

(1) C 6 H 5 .OH + CHC1 3 = C 6 H 4 < °^ a + HC1 ; 

(2 > C ^<c2ci 2 + 2Na ° H - CA< cS(OH) 2 + 2NaC1; 

< 3 > C ^<2H(OH) 2 = CA< c2o +H2a 

This reaction is of general application to phenols, and affords 
a very convenient method for the preparation of the phenol- 
aldehydes and from these the acids. 

Salicylic acid crystallizes from hot water in fine needles. It 
melts at 155° to 156°. 

When heated with soda-lime, it breaks up into phenol and 
carbon dioxide : — 

C6H4< COH = C6H5 - OH + C ° 2 - 
Heated alone it gives phenyl salicylate (salol) and xanthone: — 



PHENYL SALICYLATE. 333 

W 2C ^<C?0H = CA <c?OC 6 H 5 + CO -' + H >° ; 

Phenyl salicylate (salol). 
Xanthone. 

With ferric chloride, its aqueous solution gives a characteristic 
dark violet-blue color. Free salicylic acid is antiseptic, prevent- 
ing decay and fermentation. It is therefore used for preserving 
foods. It is also used extensively in medicine, especially in 

rheumatism. 

OH 
Salicylic acid forms salts of the general formula C 6 H 4 < C0 ^ ; 

and, with the alkalies, compounds, in which both the phenol 
hydrogen and the acid hydrogen are replaced by metals, as 

C 6 H 4 < r0 K - Salts of the latter order, which contain the metals 

of the alkaline earths, are decomposed by carbon dioxide. The 

basic calcium salt, C 6 H 4 < co > Ca + H 2 0, is very difficultly 

soluble in water. Salicylic acid forms ethereal salts of 

the general formula C 6 H 4 < r , n „, of which methyl salicylate, 
OH yjyJzR 

C 6 H 4 < / ^ rk nX r , is the best-known example. It forms, also. 
UU2L/M3 

ether-acids of the general formula o c ll 4 < r() \ I ; and, finally, 

compounds of the general formula c l5 ll 4 <qq r - 

A very large number of substitution-products and other 
derivatives of salicylic acid have been studied. 

Phenyl salicylate (salol\ OeHi < 2Sn« « . — This is 

formed when salicylic acid is heated alone fco 200-220°, and 

when salicylic acid, phenol, and phosphorus owchloride arc 
heated together. It. is a solid that melts at \:v\ it is exten- 
sively used as an antiseptic. 

That salicylic' acid belongs to the oil ho series, follows from 
the following facts : — 



334 DERIVATIVES OF THE BENZENE SERIES. 

Ortho-toluene-sulphonic acid has been converted into ortho- 
sulpho-benzoic acid, and this into salicylic acid. Further, the 
same toluene-sulphonic acid has been converted into ortho-toluic 
acid, which, by oxidation, yields phthalic acid. 



(1) 


°^<Sh w +3 ° 

Ortho-toluene-sulphonic 
acid. 


= C H < ^^H 

SOgH (o) 

Ortho-sulpho-benzoic 
acid. 


+ H 2 0; 


(2)' 


pw ^C0 2 K 
C6H4< SO s K w 


+ KOH 


p „ . C0 2 K 

Potassium salicylate. 


+ K 2 S0 8 ; 


(3) 


pu / CH 3 
C ° Ki < S0 3 K (0) 


+ KCN 


= C 6 H 4 < CHs 
CN (0) 


+ K 2 S0 3 ; 


(4) 


6 M 4 < QK 


+ 2H 2 


- teH4< C0 2 H (o) 

Ortho-toluic acid. 


+ NH 3 ; 


(5) 


pTT, ^H 3 

° 6H4< C0 2 H (0 


+ 30 


pu, C0 2 H 
- CeH4< C0 2 H (0) 

Phthalic acid. 


+ H 2 0. 



Oxybenzoie acid, 1 C H < OH This 

Meta-hydroxy-benzoic acid, J 6 4 CC>2H(m)' 
acid is made from meta-amino-benzoic and meta-sulpho-benzoic 
acid by the usual reactions. 

It crystallizes from water in needles united to form wart-like- 
looking masses. It gives no color with ferric chloride. Its 
connection with meta-phthalic (isophthalic) acid andmeta-xylene 
is shown by means of the transformations tabulated on p. 329 ; 
that is to say, the same sulpho-benzoic acid which, by melting 
with caustic potash, yields oxybenzoie acid, by melting with 
sodium formate, yields isophthalic acid. Therefore oxybenzoie 
acid is a meta compound. 

Para-oxybenzoic acid, 1 C H < OH — Para-oxv- 

Para-hydroxy-benzoic acid, i 6 4 C02H (P ) * J 

benzoic acid is formed from the corresponding amino and 



DI-HYDKOXY-BENZOIC ACIDS. 335 

sulpho-benzoic acids ; by treating various resins with caustic 
potash ; from anisic acid (which see), by heating with hydriodic 
acid ; by heating potassium phenolate in a current of carbon 
dioxide to 220°. 

Note for Student. — Notice the fact that, while sodium phenolate, 
when heated in a current of carbon dioxide, yields salicylic acid, 
potassium phenolate, under the same circumstances, yields para-oxy- 
benzoic acid. 

Its aldehyde is formed, together with salicylic aldehyde, by 
treating phenol with chloroform and caustic soda (see Exp. 76). 

The reasons for regarding para-oxybenzoic acid as a mem- 
ber of the para series are similar to those which show that 
oxybenzoic acid is a meta compound. The same sulpho-benzoic 
acid that yields para-oxybenzoic acid, also yields terephthalic 
acid. 

Anisic acid, ) ^, OCHs Anisic 

Para-methoxy-benzoic 1 acid, J ( ' 4 COjHuo' 
acid is formed by the oxidation of anethol, C C H 4 < 3 , a 

phenol ether contained in anise oil. It is made by heating 
para-oxybenzoic acid with caustic potash and methyl iodide 
and saponifying the di-methyl ether thus formed. As the 
formula indicates, it is the methyl ether of para-oxybenzoic 
acid. As will be seen, it is isomeric with methyl salicylate. 
By boiling with caustic alkali the latter is saponified, while 
anisic acid is not. When anisic arid is distilled with lime 
anisol is formed. 

Dl-HYDROXY-BENZOIC A.CIDS, C T H 6 4 . 

Protocatechuic acid, CoHa jL^J. is B frequent product 

of the fusion of organic substances with caustic potash. Thus. 
the following substances, among others, yield it : oil o( cloves, 
piperic acid, cateohin, gum benzoin, asafoetida, vanillin, etc. 

1 dfethony is derived from meftoayi, the Dame gives to the ether group, OCHj, In 

n similar way 0C 2 H a is oalled tthowy ' .• *h ,.,11,,. pAenooyi, etc 



336 DERIVATIVES OF THE BENZENE SERIES. 

It is made from sulpho-oxybenzoic acid, and from sulpho-para- 
oxy benzoic acids by fusing with caustic potash. 

Note for Student. — What analogy is there between the fact that 
protocatechuic acid is formed from sulpho-oxybenzoic acid and from 
sulpho-para-oxybenzoic acid, and the fact that pseudocumene is formed 
from brom-meta-xylene and from brom-para-xylene ? What conclusion 
may be drawn regarding the relations of the two hydroxyl groups, and 
the carboxyl in protocatechuic acid ? 

By distillation with lime, protocatechuic acid breaks up into 
pyrocatechol and carbon dioxide : — 

< 0H t OTT 

c 6 hJoh =c 6 h 4 |^ + co 2 . 

\ LU 2 ri Pyrocatechol. 

rOCHs 
Vanillic acid, CeHsJ OH > is formed by oxidation of 
ic0 2 H 

vanillin, which is the corresponding aldehyde. It is the mono- 
methyl ether of protocatechuic acid. 

/ r OCH 3 \ 

Vanillin, CsHsOs ( C 6 H 3 \ OH ) , is the active constituent 
^ 1 CHO J 

of the vanilla bean. It is made artificially by treating the 

ether, guaiacol, C 6 H 4 < 3 , with chloroform and caustic soda. 

U-tL(O) 

rCHO 
Piperonal, C 6 H 3 \ O > q Hq . — This is formed by oxidizing 

piperic acid, which is itself a product of the decomposition of 
piperine, a complex compound that is found in different 
varieties of pepper. Piperonal is the methylene ether of 
protocatechuic aldehyde. It can be made artificially, and is 
used in perfumery under the name heliotropine. The relations 
between protocatechuic aldehyde, vanillin, and piperonal are 
shown by the following formulas : — 



TANNIC ACID. 337 

( CHO (1) ( CHO (1) ( CHO (1) 

C 6 H 3 -}0H (3) C 6 H 3 J0CH 3 (3) C 6 EU CH (3) 

(OH (4) (OH (4) (0 2 (4) 

Protocatechuic Vanillin. Piperonal 

aldehyde, i (Heliotropine). 

Tri-hydroxy-benzoic Acids, C 7 H 6 5 . 

Gallic acid, CtHgOs + HsOfCeHsj^^Y —Gallic acid 

occurs in sumach, in Chinese tea, and in many other plants. 
It is formed by boiling tannin or tannic acid with dilute sul- 
phuric acid ; by melting brom-protocatechuic acid with caustic 
potash : — 

rBr 
C 6 H 2 ] (OH), + KOH = C 6 H 2 j ^ H ) 3 + KBr. 

(C0 2 H (C ° 2H 

Brom -protocatechuic Gallic acid, 

acid. 

It is best prepared from gall nuts by fermentation of the 
tannin contained in them. 

Gallic acid is difficultly soluble in cold water, easily in hot 
water, alcohol, and ether. Its solution gives, with a little 
ferric chloride solution, a bine-black precipitate, which dis- 
solves in excess of ferric chloride, forming a dark green 
solution. It readily reduces gold and silver salts in solution. 
When distilled, it yields pyrogallol (pyrogallic acid) and 
carbon dioxide : — 

C ti H 2 1 (^ = C e H 3 (OH) 8 + CO* 

Tannic acid, tannin, OuHioOs. — This substance occurs 
in gall nuts, from which it is extracted in Large quantities. It 
is an amorphous powder, [t is markedly astringent in its action 
on the mucous membranes. It is soluble in water, the solution 
giving, with ferric chloride, a dark blue-black color. Tannin is 
used extensively in medicine, in dyeing, and in the manufacture 
of ink and leather. It combines with gelatin forming an 



338 DERIVATIVES OF THE BENZENE SERIES. 

insoluble substance. Its relation to gallic acid is indicated by 
the following equation : — 

2 C 7 H 6 5 = C 14 H 10 O 9 + H 2 0. 

Gallic acid. Tannin. 

Ketones and allied Derivatives of the Benzene Series. 

The ketones of the benzene series are strictly analogous to 
those of the paraffin series, and they are made in the same way. 
Acetone is made by distilling calcium acetate : — 



CH3.COO 

cH 3 rcoo >Ca 



^ 3 >00 + CaC0 3 . 
U±i 3 

Acetone. 

So, also, benzophenone or diphenyl-ketone is made by distill- 
ing calcium benzoate : — 



CeH,GOJO 

C 6 H 5 | CO 



C 6 H 5>C0 + CaC03> 
C 6 H 5 

Benzophenone. 

Further, by distilling mixtures of the salts of two fatty acids, 
mixed ketones are obtained : — 

CH 3 . COjOMj = CH 3 co M co 
C 2 H 5 .;COOM; C 2 H 5 

, Ethyl-methyl 

ketone. 

And, similarly, mixed ketones containing one residue of a 
benzene hydrocarbon and one of a paraffin ; or, two different 
residues of benzene hydrocarbons can be obtained thus : — 

(1) C 6 H 5 .COOM = C 6 H 5>C + M 2 C0 3 ; 

K) CH 3 .COOM CH 3 2 3 ' 

Phenyl-methyl ketone, 
Acetophenone. 

C fi H,.COOM 



'•"«■— — C«H, 



(2) c H < CH 3 = ^ > CO + M 2 C0 3 . 

Phenyl-tolyl-ketone. 



^COOM 



QUINONES. 339 

Interesting results have been reached through a study of the 
oximes of the aromatic ketones. It has been shown that while 
the symmetrical ketones, like benzophenone, C 6 H 5 . CO . C 6 H 5 , 
give but one oxime, some of the unsymmetrical ketones, like 
phenyl-tolyl-ketone, C 6 H 5 . CO . C 6 H 4 . CH 3 , give two. This is 
quite in accordance with the views already set forth in regard to 
the stereochemistry of nitrogen compounds (see Benzaldoxime, 
page 314). In the terms of stereochemistry the two formulas 

C 6 H 5 . C . C 6 H 5 C 6 H 5 . C . C 6 H 5 

II and || 

HO.N N.OH 

are identical, so that a symmetrical ketone can give but one 
oxime. On the other hand the formulas 

C 6 H 5 . C . C 6 H 4 . CH 3 C 6 H 5 .C.C 6 H 4 .CH 3 

II and || 

HO.N N.OH 

are different, so that an unsymmetrical ketone can give two 
oximes. 

QUTNONES. 

The quinones are peculiar bodies which in some ways are 
allied to the ketones. The simplest example of the class, and 
the one best known, is called quinone. Its formula is (\ ; H 4 0., 
and it therefore appears to be benzene in which two hydrogen 
atoms are replaced by two oxygen atoms. All quinones bear 
this relation to the hydrocarbons, of which they may be regarded 
as derivatives. 

Quinone, CeEUOa, is formed by the oxidation of quinic acid, 
hydroquinol, para-diamino-benzene, and some other benzene 
derivatives in which two substituting groups occupy the para 
position relatively bo each other. 

It is usually made by oxidizing aniline with sodium bi- 
chromate and sulphurio acid. In the laboratory it is most 
convenient to make it by oxidizing hydroquinol. 



340 



DERIVATIVES OF THE BENZENE SERIES. 



It forms long, yellow prisms ; sublimes in golden-yellow 
needles ; is volatile with steam ; and lias a peculiar penetrating 
odor. 

Sulphurous acid reduces quinone to hydroquinol : — 

C 6 H 4 2 + 2 HI = C 6 H 4 (OH) 2 + 2 1. 

The easy transformation of hydroquinol into quinone, and 
the opposite transformation of quinone into hydroquinol, as 
well as the formation of quinone from other para compounds, 
force us to the conclusion that the oxygen atoms in quinone 
are in the para position relatively to each other. Quinone 
appears, therefore, as benzene containing two oxygen atoms in 
the para position as represented in the formula : — 

CO 
HC/^CH 



HC 



CH 



CO 



As quinone forms a dioxime, and takes up four atoms of 
bromine and of chlorine, and two molecules of hydrochloric 
and of hydrobromic acid, most chemists regard it as a diketone 
of the formula : — 

CO 



HC 



CH 



HC' .CH 

CO 

According to this view quinone is not, strictly speaking, a 
derivative of benzene, but is derived from dihydrobenzene : — 

CH 2 



HC 
HC 



CH 
CH 



CH, 



PYRIDINE BASES. 341 

The easy changes from quinone to hydroquinol and from this 
back to quinone are not easily understood if this view is correct. 

It has been suggested that quinone may be analogous to the 
peroxides, having its two oxygen atoms combined with each 
other thus : — 

C 



HC 

6. 

c 



HC 



CH 
CH 



This represents quinone as a true derivative of benzene, and 
if it is analogous to the peroxides, it should be a strong oxidiz- 
ing agent, as it is. 

If the di-ketone formula is correct quinone may be regarded 
as derived from a dibasic acid in the same way that a simple 

ketone is derived from a monobasic acid. Thus, the calcium 

POOH 
salt of an acid of the formula C 2 H 2 < rooII ought, according 

to this view, to yield quinone by distillation : — 



CO;0 n j 
C 2 H 2 <.---' >Ca! 

COO I co 

'--".-.v."-; = C 2 H 2 < ^ > C 2 H a + 2 CaCO s . 

C 2 H 2 <^ J°>Cai 
|COO ! 

Several quinones have been studied. Under the head of 
Anthracene we shall meet with an important one called anthra- 
quinone, which has been made by reactions that prove it to be 
a di-ketone in the sense in which this expression is explained 
above. 

Pyridine Bases, C„nx,„_,!Sr. 

The pyridine bases are termed in the distillation of bones, 
certain bituminous shales, and coal, and were first isolated from 



342 DERIVATIVES OF THE BENZENE SERIES. 

bone oil, which, is a complex mixture of many substances. At 
present these bases are obtained principally from coal tar. The 
principal members of the group are pyridine, picoline, lutidine, 
and collidine. They form an homologous series : — 

Pyridine C 5 Jl^ 

Picoline C 6 H 7 N 

Lutidine C 7 HJS 

Collidine C 8 H n N 

The formation of these bases in the distillation of bones is 
due to the presence of acrolein, ammonia, methylamine, etc., 
and their action upon one another at high temperatures. 
Members of the series are formed whenever aldehydes of the 
fatty series are heated with ammonia. For example, ordi- 
nary aldehyde and ammonia give methylethylpyridine, C 8 H U N, 
C 5 H 3 (CH 3 )(C 2 H 5 )N:- 

4 C 2 H 4 + M 3 = C 8 H U N + 4 HoO ; 

and acrolein and ammonia give /3-picoline : — 

2 C 3 H 4 + NH 3 = C 6 H 7 K + 2 H 2 0. 

Further, pyridine and picoline are formed when glycerol is 
distilled with ammonium sulphate and sulphuric acid. 

Pyridine, C5H5N. — Pyridine is found in commercial am- 
monia, and is formed, as stated above, in the distillation of 
bones, of certain bituminous shales, and of coal. It has been 
prepared from a number of its carboxyl derivatives, as, for 
example, from nicotinic acid, C 5 H 4 N . C0 2 H, which is formed 
when nicotine is oxidized with nitric acid. The formation of 
P3^ridine from quinolinic acid, a dicarboxyl derivative of pyri- 
dine, is of special importance as it leads very clearly to a con- 
ception of the constitution of pyridine. Quinoline (which see) 
will be shown to have the constitution represented by the 
formula 



PYRIDINE. 



343 



HC „ CH 



HC 
HC 



\/c\/ 

N CH 



CH 
CH 



When it is oxidized it gives the dibasic acid above referred to, 
quinolinic acid, 

CH 



HC/ 
Hcl 



QA 

I 



N 



C\C0 2 H 



When this is distilled with lime it loses carbon dioxide and 
gives pyridine : — 

CH 

4- 2 CO., 



CH 



HC 
HC 



C /COoH 



N 



C\CO,H 




CH 



According to this, pyridine is benzene containing a nitrogen 
atom in place of one of the CH groups. The question in re- 
gard to the linkage of the groups and atoms in pyridine is a 
difficult one to deal with, and it need not be discussed here. 
Suffice it to say that the above hypothesis, as to the relation 
between benzene and pyridine, is in accordance with all the 
facts known. 

Pyridine is a liquid with a peculiar, sharp characteristic 
odor. It boils at 136°. It acts like a monacal base, forming 
salts like C 6 H 6 E . HC1, C,H,N . 11ND, C,ll,N . ll,SO v ete. It 
unites with alkyl iodides like methyl iodide, ethyl iodide, ete. 
When these compounds are treated with silver hydroxide, they 
form the corresponding hydroxides which are strong bases. 
The compounds with the alkyl iodides are converted by heat 



344 DERIVATIVES OF THE BENZENE SERIES. 

into salts of homologues of pyridine. For example, the ethyl 
iodide addition-product of pyridine is transformed at 290° into 
ethylpyridine hydriodide : — 

C 5 H 5 N . C 2 H 5 I = C 2 H 5 . C 5 H 4 N . HI. 

The view above presented has suggested various lines of in- 
vestigation. Thus, if the above formula represents the rela- 
tions between benzene and pyridine, it is clear that the existence 
of three isomeric mono-substitution products of pyridine ought 
to be possible. Thus, there should be three methyl-pyridines 
or picolines, three pyridine-carbonic acids, etc. The three 
picolines should correspond to the formulas 

H H 9 Hs 

HC/ ^CH HC/ \c.CH 3 He/ \cH 

I I II I I 

HCv /C.CH 3 HCy /CH HCv /CH 

\^/ \^/ \N/ 

Ortho-picoline. Meta-picoline. Para-picoline. 

All three picolines are known ; and, by oxidation, they are 
converted into the three pyridine-carbonic acids, C 5 H 4 N.C0 2 H; 
and these, when distilled with lime, yield pyridine and carbon 
dioxide. 

Lutidines, CsHaCCEkOaN. — No less than six isomeric vari- 
eties of dimethylpyridine are possible according to the theory. 
Five of these have been prepared in pure condition. By oxida- 
tion they yield, first, monobasic acids, and then dibasic acids. 
When the monobasic acids are distilled with lime, they yield 
picolines. The dibasic acids give pyridine : — 



CH 3 ath XT ^ CH 3 -™ tt ^ C0 2 H # 

CH 3 ^ N ° 5Hs< C0 2 H ^ ^ UH3< C0 2 H' 



NC 5 H 3 < CH3 = NC 5 H 4 . CH 3 + C0 2 ; 
NC 5 H 3 < f° 2 ^ = NC 5 H 5 + 2 C0 2 . 



CONINE. 



345 



Conyrine, Propylpyridine, NO5H4 . C3H7. — This base is 
formed when conine is heated with zinc chloride or when the 
hydrochloride of conine is heated with zinc dust. It is con- 
verted into picolinic acid by oxidation, and is reduced to conine 
by hydriodic acid. 

The pyridine bases unite with two, four, or six atoms of 
hydrogen. Some of the alkaloids are derivatives of the addi- 
tion-products thus formed. 

Piperidine, CsHnN. — This base is formed from pipeline, a 
constituent of pepper. It has been made by adding hydrogen 
to pyridine by means of sodium and alcohol : — 
C 5 H 5 N + 6 H = C 5 H n K 



Conine, Propylpiperidine, CH2 



CH2-CH-C3H7 

)NH . — This 
\CH2-CH2 

base occurs together with others in hemlock (Con ium maculatu m). 
It is a colorless liquid, and is a violent poison. This is the 
first alkaloid that was prepared artificially, and it is therefore 
of special interest. The steps taken are indicated below : — 



CH.OH 

I 

CHOH 
I 
CH 2 OH 

Glycerol. 

CH 2 .CONH 2 

I 
CH 2 

I 
CH 2 .COMI, 

N 
HC/\CH 



CHoBr 

I 
>- CH 

II 
CH 2 

Allyl bromide. 



CHoBr 

I 

CH, 

I 

CH 2 Br 

Trimethylen 

bromide. 



CH 2 CN 

I 

CH a — >- 

I 

CH 2 CN 

Trimethyleoe 
03 anlde. 



CH^CIIoNH.. 

I 

CH., 

I 

(MI,. (MI.,. Ml 
lVntMuu'iin lene diamlo 

(MI. -N I 



(MI.,. (MI. 



^ (MI. 

I 



Ml 



/ 



\\C 



(MI 



(MI 
Pyridine. 



lie 



IK 



(Ml 



(Ml, .(Ml.. 
Piperidine, 

\ 

IK 1 , \\(M1 



(Ml 



IK 



CH 



(Ml 



CH 



346 DERIVATIVES OF THE BENZENE SERIES. 



HC 



N NH 

Nc.CH = CH.CH 8 H 2 C 

ICH H 2 C 



CH CH 



CH.CH 2 .CH 2 .CH 3 
CH 2 



Inactive Conine. 

The change from picoline to allyl-picoline is effected by 
means of paraldehyde. The conine thus obtained is optically 
inactive, whereas that obtained from hemlock is dextro-rotatory. 
By means of the salt with d-tartaric acid, the inactive conine 
can be resolved into the two active varieties. The tf-conine 
thus obtained is identical with natural conine. 

[Is there an asymmetric carbon atom in conine ?] 

Terpenes. 

Terpenes are hydrocarbons found in various coniferous trees. 
The volatile oil from these trees consists of hydrocarbons of 
the composition C 10 H 16 . The ethereal oils that are obtained by 
distilling fruits of many citrus varieties with water have the 
same composition. In some oils obtained from natural sources 
terpenes are found mixed with other substances, especially 
such as contain oxygen. 

The terpenes can be classified into : — 

(1) Terpenes, C 10 H 16 ; 

(2) Sesquiterpenes, C 15 H 24 ; 

(3) Diterpenes, C^H^; 

(4) Polyterpenes, (C 10 H 16 ) X . 

All of these hydrocarbons are related to hexahydrocymene, 
CH 2 CH 2 
CH 3 Hc/~ \CH . CH(CH 3 ) 3 . 
CH 2 CH 2 
This is shown by the fact that many of the terpenes are 



GERANIOL. 347 

converted by gentle oxidation into cymene, and by oxidation 
with, nitric acid into p-toluic and terephthalic acid. 

Some of the terpenes take up one molecule of hydrochloric 
acid, others take up two molecules. They also combine with 
water and form hydrates. They are easily polymerized by 
heat or by shaking with sulphuric acid or with boron fluoride. 

The terpenes proper of the formula, C 10 H 16 , may be con- 
veniently divided into three groups : — 

1. Olefln-terpene Group ; 

2. Terpane or Menthane Group ; 

3. Camphane Group. 

1. Olefin-terpene Group. 

These compounds are not themselves derivatives of hydro- 
cymene, but they are easily converted into such derivatives. 
They are unsaturated paraffins. The only ones that need be 
mentioned here are isoprene, C 5 H 8 , and anhydrogeraniol, C 10 H lt5 . 
The former is an example of a Jiemiterpene. It is formed iu 
the distillation of caoutchouc. It is probably metJu/1-divinyl, 
CH 3 v 

C - CH = CH 2 . 

ch/ 

Anhydrogeraniol is formed from geraniol, C 10 H ls O. (which 
see) by elimination of water. It probably has the structure 
represented by the formula 

(CH 8 ) a C=CH.CH a .CH 2 .C(CH 8 )=C=CH 2 . 

As will be seen, it contains three double bonds. It has the 
power to take up six atoms o\' hydrogen or of bromine. 

Geraniol, CioHisO, is contained in Indian oil of geranium 
and in a number of other ethereal mis. Its properties show- 
clearly that it is a primary alcohol. By oxidation with chromic 
acid it gives an aldehyde, gemnial, C 10 H ie O 3 and an acid, geranic 
acid, C 10 H 16 O a . Geranial loses water and gives cymene: — 



348 DERIVATIVES OF THE BENZENE SERIES. 

CH(CH 3 > CH(CH 3 ) 2 

I I 

CH 9 C 

\ s \ 

OHC CH HC CH 

I II = I II +H 2 0. 

HC CH HC ,CH 

V V 

I I 

CH 3 CH 3 

2. Terpane or Menthane Group. 

Tlie characteristic property of the members of this group is 
their power to take up four atoms of bromiue or two molecules 
of hydrochloric or of hydrobromic acid. 

Limonene, Dipentene, CioHie. — This is known in three 
varieties — dextro, levo, and inactive. The inactive variety 
occurs with cineol in Oleum cince, and is formed by heating 
pinene and camphene to 250-300°, and is therefore contained 
in Russian and Swedish oil of turpentine. c?-Limonene is 
found in oil of citron, oil of bergamot, and a number of 
other ethereal oils. With bromine it forms a tetra-bromide, 
C 10 H 16 Br 4 , that melts at 104-105°. Z-Limonene is found in the 
oil of fir needles (Pinus sylvestris) and in oil of fir, together 
with Z-pinene. 

Limonene probably has the constitution represented by the 

formula 

CH 3 

I 
C 

I I 

H 2 C CH 2 



H 9 C 



W 

I 
CH 3 — C = CH 2 



CAMPHENE GROUP. 349 

^■Menthol, CioHi9(OH), is a solid, melting at 42° and boil- 
ing at 212°. It is the chief constituent of oil of peppermint. 
It is a hydroxyl derivative of hexa-hydrocymene, C 10 H 20 . 

3. Camphene Group. 

The two most important members of this group are pinene 
and camphene. Among the oxygen derivatives of camphene 
is camphor. 

Pinene, CioHie. — This is the principal ingredient of the 
various kinds of oil of turpentine obtained from different varie- 
ties of pine. It also occurs in a number of ethereal oils. It 
combines with one molecule of hydrochloric or of hydrobromic 
acid; with two atoms of bromine; and with one molecule of 
water. When heated to 250-270° it is converted into an 
isomeric hydrocarbon dipentene (limonene). Pinene is known 
in three varieties : dextro-, levo-, and inactive. rZ-Pinene is 
obtained from American oil of turpentine; Z-pinene from the 
French. The inactive variety is formed by combination of 
the two active varieties. 

Pinene contains one double bond, as is shown by its union 
with one molecule of hydrobromic acid, and with two atoms o( 
chlorine and of bromine. The constitution of pinene lias not 
been definitely determined. 

rf-Pinene hydrochloride, CioHnCl, is formed by conducting 

dry hydrochloric acid gas into pinene. It is a crystalline solid 
with an odor like that of ordinary camphor. It is called arti- 
ficial camphor. When heated alone, or with bases, hydrochloric' 
acid is split off and a hydrocarbon isomeric with pinene is 
formed. This is camphene. 

Oil of Terpentine, When incisions arc made in the trunk 

of various conifers, a liquid exudes which is known as turpen- 
tine. Most o\' that which comes into the market is obtained 
from Pinus australiSy crowing in North America. The volatile 



350 DERIVATIVES OF THE BENZENE SERIES. 

constituent of turpentine is oil of turpentine. The other is 
abietic acid. These are separated by distillation. If the distil- 
lation is carried on without the addition of water, the residue 
is ordinary rosin (colophony). 

Oil of turpentine dissolves sulphur, phosphorus, and caout- 
chouc, and is used in the preparation of varnishes and oil colors. 

Camphene, CioHie. — This terpene is formed from borneol 
(which see) by heating it with acid potassium sulphate and by 
treating it with other reagents. There are several varieties of 
camphene known. It has already been stated that a camphene 
is formed by the elimination of hydrochloric acid from the 
hydrochloric acid addition-product of Z-pentene. That which 
is thus obtained is known as Z-camphene or terecamphene. 
Similarly a d-camphene is obtained from the pinene obtained 
from American oil of turpentine. Camphene has been shown 
to have the constitution represented by the formula, — 

CH 2 — CH — CH 

I 
CH 3 — C — CH 3 

CH 2 — C — CH 

I 
CH 3 

It is closely related to camphor, as will be pointed out. 

Camphors. 

Borneol, Borneo Camphor, CioHisO. — Borneo camphor 
is found in cavities in a tree (Dryobalanops camphord) that 
grows in Borneo, Sumatra, etc. This variety is dextro-rotatory. 
The levo-rotatory variety is found in the camphor from valerian 
oil, and inactive borneol is formed by bringing together d- and 
Z-borneol. Borneol is much like ordinary camphor or lanrinol, 
but its odor resembles that of pepper. When laurinol is treated 
with sodium and alcohol, it gives both d- and Z-borneol : — 



CAMPHOR. 351 

2 C 10 H 16 O + 4H = C 10 H 18 O + C 10 H 18 O. 

Laurinol. rf-Borneol. J-Borneol. 

Both of the active varieties are oxidized to laurinol by nitric 
acid. Borneol is an alcohol, a,s is shown by the action of 
phosphorus pentachloride and of glacial acetic acid. The 
former gives the chloride, C 10 H 17 C1 : — 

C 10 H 17 (OH) + PC1 5 = C 10 H 17 C1 + POCI3 + HC1. 

The latter gives an acetate : — 

C 10 H 17 (OH) + HOOC . CH 3 = C 10 H 17 O . OC . CH 3 + H 2 0. 

Camphor, laurinol, CioHieO. — This is the substance ordi- 
narily called camphor. It is obtained in China and Japan 
from different species of the genus Camphora of the Laurus 
family by distilling the finely cut wood with water vapor. It 
is purified by sublimation. It is a colorless mass that can be 
crystallized from alcohol and sublimes in lustrous prisms. The 
ordinary form is dextro-rotatory. Both the other possible 
stereo-isomeric forms are known. Camphor is reduced to 
borneol by hydrogen from sodium and alcohol. It can be 
made by oxidizing borneol or camphene. When distil led with 
phosphorus pentoxide, camphor gives cymene : — 

C 10 H 18 O = C 10 H 16 + H 2 O. 

The same decomposition is effected by heating camphor with 
concentrated hydrochloric acid to L70°. 

All the evidence goes to show that camphor is not an alcohol. 
but a ketone. The ease with which it- is converted intooymene 
makes it. highly probable that a methyl group and an isopropy] 
group are present in the compound in the para position in a 
benzene ring. It forms earvacrol by loss of two atoms o( 
hydrogen. Carvaorol is isomeric with thymol, the hydroxy 1 
being in the ortho position to the methyl group as shown in 
the formula, — 



352 DERIVATIVES OF THE BENZENE SERIES. 

C 3 H 7 

I 

HC/ \CH 

I I 

HCv /C(OH) 
\/ 
I 
CH 3 

This makes it appear highly probable that the oxygen in 
camphor is ortho to methyl. Other facts that have been 
brought to light in investigations of the oxidation-products of 
camphor indicate that the group, C(GH.^) 2 j formed from iso- 
propyl is united with two para carbon atoms of the benzene 
ring. All this is shown by the formula for camphor now 
perhaps generally accepted by chemists : — 



H 



,c/ 



yCh 



*CH S 



| H3C.C.CH3 I 
H 2 C V i /CO 



c 



CH 3 

The relation between borneol, camphor, and camphene is 
shown by the formulas, — 

•CHv /CHv yCHv 

H 2 c/ ^CHa H 2 c/ \CH 2 H 2 c/ ^CH 

I H3C.C.CH3 I I H3C.C.CH3 I I H3C.G.CH3 II 

H 2 Cv .CO H 2 C. .CH(OH) H 2 Cv ,CH 

\fc/ \fc/ \fc/ 

CH 3 CH 3 CH 3 

Camphor. Borneol. Camphene. 



CHAPTER XVI. 

DI-PHENYL-METHANE, TRI-PHENYL-METHANE, 

TETRA-PHENYL-METHANE, AND THEIR 

DERIVATIVES. 

As we have seen, toluene may be regarded either as methyl- 
benzene or phenyl-methane. Of course, according to all that 
is known regarding similar substances, the two views are identi- 
cal. Regarding it, for our present purpose, as phenyl-methane, 

r C 6 H 5 

TT 

we may write its formula thus : c 1 H 

I H 
This suggests the possibility of the existence of such sub- 
stances as 

r c 6 h 5 

('TT 

Di-phmyl-methane C < 6 :> , 

MI 

CV.II:, 

TH-phenyl-methane . . . . . . C \ ,! \ 




and Tetra-phenyl-methane 

ii 

All these hydrocarbons are known. The derivatives of tri- 
phenyl-inethane are o( special tnteresl ami importance. 
There is one reaction by moans of which those hydrocarbons 



354 DI-PHENYL-METHANE, ETC. 

can be made very readily. It has also been used for the synthe- 
sis of many other hydrocarbons. It depends upon the remarkable 
fact that, when a hydrocarbon is brought together with a com- 
pound containing chlorine, and anhydrous aluminium chloride 
then added, hydrochloric acid is evolved, and union of the two 
substances is effected, the aluminium chloride not entering into 
the composition of the product. Thus, when benzene and 
benzyl chloride, C 6 H 5 .CH 2 C1, are brought together under ordi- 
nary circumstances, no action takes place ; but, if some solid 
aluminium chloride is added, reaction takes place according 
to the following equation : — 

C 6 H 5 .CH 2 C1 + C 6 H 6 = C 6 H 5 .CH 2 .C 6 H 5 + HC1, 

Di-phen yl-me thane . 

and di-phenyl-methane is formed. 

Similarly, when chloroform and benzene are brought together 
in the presence of aluminium chloride, tri-phenyl-methane is 
formed according to this equation : — 

CHC1 3 + 3 C 6 H 6 = CH(C 6 H 5 ) 3 + 3 HC1. 

Tri-phenyl-methane. 

Another method by which these hydrocarbons can be made, 
consists in heating a chloride and a hydrocarbon together in the 
presence of zinc dust. Thus, benzyl chloride and benzene give 
di-phenyl-methane when boiled with zinc dust ; and benzal 
chloride, C 6 H 5 .CHC1 2 , and benzene give tri-phenyl-methane : — 

C 6 H 5 .CHC1 2 + 2 C 6 H 6 = CH(C 6 H 5 ) 3 + 2 HC1. 

)nly tri-phenyl-methane will be treated of here. 

Tri-phenyl-methane, 19 H 16 [=OH(0 6 H 5 ) 3 ]. — This hydro- 
carbon can be made, as above described, from benzal chlo- 
ride and benzene, and from chloroform and benzene. It 
can also be made from benzal chloride and mercury diphenyl, 
HgCCeH^:- 

C 6 H 6 .CHC1 2 + Hg(C 6 H 5 ) 2 = CH(C 6 H 5 ) 3 + HgCt 



TRIPHENYL-METHANE DYES. 355 

It forms lustrous, thin laminae, which melt at 92°. It is 
insoluble in water ; easily soluble in ether and chloroform. It 
is crystallized best from alcohol. 

Towards reagents it is very stable. Thus, ordinary concen- 
trated sulphuric acid does not act upon it. r C 6 H 5 

I /~1 IT 

Oxidizing agents convert it into tri-phenyl-carbinol, C \ J 5 * 

I OH 
That the oxidation-product is really tri-phenyl-carbinol appears 
probable, from the fact that whenever aromatic hydrocarbons 
that contain paraffin residues are oxidized, the paraffin resi- 
dues are first attacked, while, as a rule, the benzene residue is 
unacted upon. Further, it gives an acetate with acetyl chlo- 
ride; and with phosphorus pentachloride it gives a chloride 
which is decomposed by boiling water, giving the carbinol 
again. A bromide is formed by treating it with hydrobromic 
acid, and this gives the carbinol when boiled with water. 

Tr m 1 e t th°;ne Phenyl " } OuHuOTOOrf = CH(C.H 4 NO,) 8 ], is 
formed by treating triphenyl-methane with nitric acid ; and 
also by treating a mixture of nitro-benzene and chloroform 
with aluminium chloride : — 

CHCI3 + 3 C fl H 5 . NO, = CH(C G H 4 . NO,) ;! + 3 HC1. 
This reaction shows that in the tri-nitro product 0110 nitro group 
is contained in each benzene residue. 

Triamino-triphenyl-methane, para-leucaniline, 

Ci,.Hi ;! (NH..) ;i [= OH(OeH4.NH2)8]. 
The tri-amino compound is made by reduction of the tri-nitro 
compound, and also by reduction of para-rosaniline. It is 
converted into para-rosaniline by oxidation. 

Triphenyl-methane Dyes. 

The well-known substances included under the bead ^( Tri- 
phenyl-methane Dyes are more or less simple derivatives o{ 
the two compounds oallecl roscmiline andjxira-rosantftna, 



356 



DI-PHENYL-METHANE, ETC. 



When mixtures of aniline and the toluidines are heated to- 
gether with different oxidizing agents, such as arsenic acid, 
stannic chloride, mercuric chloride, etc., several substances are 
formed, the principal of which are the two above named. Para- 
rosaniline, C 19 H 19 lSr 3 0, is formed from para-toluidine and aniline, 
according to the equation, — 

2 C 6 H 7 N + C 7 H 9 N +30 = C 19 H 19 N 3 + 2 H 2 0. 

Aniline. _p-Toluidine. Para-rosaniline. 

Rosaniline, C 20 H 21 N 3 O, is formed in a similar way : — 



C 6 H 7 N + 2 C 7 H 9 N + 30 

Aniline, o- and ^-Toluidines. 



C 20 H 21 N 3 O + 2 H 2 0. 

Rosaniline. 



The composition and modes of formation of the two sub- 
stances show that rosaniline is a homologue of para-rosaniline, 
the relation between the two substances being represented by 
the formulas C 19 H 19 N 3 and C 19 H 18 (CH 3 )N 3 0. 

By treating para-rosaniline with a reducing agent, it is con- 
verted into para-leucaniline, which has been shown to be tri- 
amino-triphenyl-m ethane : — 



C 19 H 19 N 3 0+H 2 = C 19 H 19 N, 

Para-rosani- Para-leuc- 

line. aniline. 



= c 



C 6 H 4 
C 6 H 4 



M 2 



+ H 2 0. 



C 6 H 4 . NH 5 
IH 

It will thus be seen that para-rosaniline and rosaniline, which 
are the fundamental compounds of the group of aniline dyes, 
are derivatives of the hydrocarbon tri-phenyl-methane. 

Para-rosaniline, C19H19N3O. — The formation of this sub- 
stance by oxidation of para-leucaniline and of a mixture of 
toluidine and aniline was mentioned above. The relation 
between para-rosaniline and para-leucaniline is probably ex- 
pressed by the following formulas : — 

C 6 H 5 f C 6 H 4 . NH 2 f C 6 H 4 . NH 2 

C«H, CH \ C 6 H 4 . NH 2 C(OH) j C 6 H 4 . M, 
C 6 H 4 . NH 2 



CH 



C 6 H 5 



Tri-phenyl- 
methane. 



Triamino-triphenyl-methane, 
or Para-leucaniline. 



I C 6 H 4 . NH 2 

Triamino-triphenyl-carbinol, 
or Para-rosaniline. 



ROSANILINE. 357 

Rosaniline, C20H21N3O. — This is the principal constituent 
of commercial fuchsine. It is formed by oxidizing a mixture of 
aniline and ortho- and para-toluidines : — 

C 6 H 7 N + 2 C 7 H 9 N + 30 = C 20 H 21 N 3 O + 2 H 2 0. 

Experiment 77. In a dry test-tube put a little dry mercuric chlo- 
ride and a few drops of commercial aniline. Heat over a small flame. 
Dissolve the product in alcohol, with the addition of a little hydro- 
chloric or acetic acid. The beautiful color of the solution is due to the 
presence of the hydrochloride or acetate of rosaniline. 

On the large scale, the oxidizing agent used is arsenic acid. 
Care is taken to remove all arsenic acid from the product, but 
it is nevertheless sometimes found in the products obtained in 
the market. Mtro-benzene is also used as the oxidizing agent. 
In this case there is, of course, no arsenic in the product. 
Rosaniline crystallizes in needles or plates. It is very slightly 
soluble in water; more readily soluble in alcohol. It forms 
three series of salts with monobasic acids. With hydrochloric 
acid it forms the salts C 20 H 11} N ; . . HC1 and C M H 19 N». 3 HC1. 
The former is the substance known as fuchsine, though some of 
the fuchsine met with in the market is the acetate of rosaniline, 
C 20 H 19 N 3 . C 2 H 4 2 . The formation of the salts of para-rosaniline 
takes place as represented in the following equation : — 

fC e H 4 .NH, 

C(OH)(C 6 H 4 . NH 2 ) S + HC1 = C\II 4 . Nl I,. 

Para-rosaniline. I I C,l I , . N 1 1 . HC1 

1 I 

Para rosaniline hydrochloride. 

Instead of the formulas here given for the salt two others 
have been suggested. In one of these the salt is represented 
as derived from the base triamino-triphenyl-carbinol or para- 
rosaniline as potassium chloride is formed from potassium 

hydroxide: — 

NH 8 .C e H 4 ] Ml,.c\ ; ll (1 

NH,.C,U, U\OH) NH..(\ ; ll t [COL 

Nll-.C,!!, I NH...(\ 5 1I 4 ' 



358 DI-PHENYL-METHANE, ETC. 

According to the other view the salt and all the colored salts 
derived from para-rosaniline and similar bases have a constitu- 
tion similar to that of qninone as shown thus for the hydro- 
chloric acid salt of para-rosaniline : — 

H 2 N.H 4 C 6V /C 6 H 4 .M 2 

II 

c 

HC/NCH 

or (C 6 H 4 ]SrH 2 ) 9 C = C 6 H 4 = NH 2 C1. 
CH 



HC 



c 



NH 2 C1 

Fuchsine and the other salts of rosaniline dye wool and silk 
directly. For dyeing cotton cloth, however, a mordant is gen- 
erally necessary. 

Dyeing. Animal fibres, in general, are colored directly by 
dyes ; that is to say, they have the power of forming with the 
dyes stable compounds which adhere to the fibres. This is not 
generally true of vegetable fibres, as cotton cloth and linen. 
Hence, in order to dye the latter, something must be added 
that, with the dye, forms a compound which adheres to the 
fibres. Substances which act in this way are called mordants. 
Among the substances used as mordants are aluminium acetate, 
ferric acetate, and some salts of tin. 

Experiment 78. Make a dilute solution of picric acid by dissolving 
2s to 3s in 200 cc to 300 cc water. In a portion of it suspend a few pieces of 
white yarn or flannel. The woollen material will be strongly dyed yellow. 
In another portion suspend a piece of ordinary cotton cloth. 

It should be noted that some dyes are applicable to cotton 
without mordants. These are called substantive dyes. 

Acid fuchsine is a sulphonic acid of rosaniline. It is 
formed by treating rosaniline with concentrated sulphuric acid 
at 120°. It is soluble in water, and is a valuable dye. 



HEXAMETHYL PARA-ROSANILINE. 359 

Aniline dyes. — By introducing various hydrocarbon resi- 
dues into para-rosaniline or rosaniline, in place of some or all 
of the hydrogen atoms of the amino groups, dyes of other 
colors are formed. The general effect of introducing methyl 
groups is to form dyes of a violet color. As the number of 
methyl groups increases, the product has a deeper blue tint. 

Hexamethyl-para-rosaniline. — The hydrochloric acid 
salt of this is the well-crystallized dye, crystal violet, 
[C 6 H 4 . N(CH 3 ) 2 ] 2 C : C 6 H 4 : N(CH 3 ) 2 C1. It is one of the prin- 
cipal constituents of methyl violet. Some of the methods used 
in preparing this dye are of special interest. It is made : — 

(1) By the action of para-tetra-methyl-diamino-benzophenone 
on dimethyl-aniline in the presence of dehydrating agents : — 

^;)5:c:Si> co+c ^- n ( ch ^ hci = 

C 19 H 12 N 3 (CH 3 ) (1 C1 + H 2 0. 

(2) By heating dimethyl-aniline with carbonyl chloride and 
aluminium chloride or zinc chloride : — 

COCl 2 + 2 C 6 H 6 .N(CH 8 ) 2 = CO < ^'W' + 2 HC1; 

C 19 H 12 Ns(CH 8 ) 6 Cl + H 2 a 

Methyl violet consists of crystal violet mixed with products 
containing a smaller number of methyl groups. 

Methyl green, is an addition product formed by the action of 
methyl chloride on an alcoholic solution oi' methyl violet. 

Hofmann's violet (Dahlia) is either the hydrochloric acid or 
acetic acid salt o{ tri-methyl-rosaniline. It is made by heating 
together a, salt of rosaniline, methyl iodide, and methyl alcohol. 

Aniline blue is the hydrochloride o\' tri-phenyl-rosaniline. It 
is formed by heating salts oi' rosaniline with aniline and some 
benzoic acid. 

Soluble blue is a. sulphonio acid of aniline blue. 



360 DI-PHENYL-METHAKE, ETC. 

Phthaleins. 

In speaking of phthalic anhydride, it was stated that when 
this substance is treated with phenols, phthale'ins are formed ; 
and, in speaking of resorcinol, a markedly fluorescent body was 
mentioned as being formed when phthalic acid and resorcinol 
are heated together. 

Phenol-phthalein, C20H14O4. — This substance is formed by 
heating a mixture of phenol and phthalic anhydride with sul- 
phuric acid or some other dehydrating agent : — 

2 C 6 H 6 + C 8 H 4 3 = C^A + H 2 0. 

Phenol. Phthalic Phenol- 

anhydride, phthalein. 

The fused mass is dissolved in caustic soda, and the phenol- 
phthalei'n precipitated by the addition of an acid. It forms a 
granular crystalline powder. Its solution in alkalies is red or 
violet, according to the thickness of the layer. Acids destroy 
the color. Hence it may be used as an indicator in alkalimetry 
as a substitute for litmus. 

Phenol-phthalein, like rosaniline, is a derivative of tri-phenyl- 
methane, as has been shown by the following somewhat compli- 
cated reactions : — 

The chloride of phthalic acid, or phthalyl chloride, C 8 H 4 2 C1 2 , 
when treated with benzene in the presence of aluminium chlo- 
ride, gives up its two atoms of chlorine, and in their place 
takes up two phenyl groups, thus : — 

C 8 H 4 2 C1 2 + 2 C 6 H 6 = C 8 H 4 2 (C 6 H 5 ) 2 + 2 HCL 

Phthalyl chloride. Diphenyl-phthalide. 

The substance thus formed is known as diphenyl-phtlialide. 
Its conduct towards water and bases is such as to show that it- 
is the anhydride of an acid : — 

C 8 H 4 2 (C 6 H 5 ) 2 -f- H 2 = C 8 H 6 3 (C 6 H 5 ) 2 



PHENOL-PHTHALEIN. 361 

When this acid is reduced by means of zinc dust it loses 
oxygen : — 



C 7 H 5 J 



C0 2 H _ p tt ( C0 2 H 
(C 6 H 5 ) 2 -° lH n(C 6 H 5 ) 2 + U - 



And, finally, when the last product is distilled with baryta, 
it loses carbon dioxide and yields tri-phenyl-methane : — 

( CCi TT ( C 6 H 5 

C 7 H 5 i ^ = CH ] C 6 H 5 + C0 2 . 

We have thus passed from phthalic anhydride to triphenyl- 
methane, and the reactions just referred to are in all prob- 
ability correctly represented by the following formulas and 
equations : — 

C 6 H 5 r C 6 H 5 

C 6 H 5 4. H O = C < ^6^s 
CeH^CO^ 2 I C 6 H 4 .C0 2 H. 

L I OH 

Diphenyl-phthalide, or an- Tri phony 1-oarbinol- 

hydride of triphenyl-car- carbonic acid, 

binol-carbonic acid. 

C 6 H 5 r C 8 H 5 



C 6 H 4 . C0 2 H 
OH 



= c J C e H a 
"1 C 6 H 4 .C0 2 H 

I H 

Tripheny] -metbane- 
oarbonio add. 

rC„H« 

I 11 

Tripbenj l-metbane. 

Now, by making dinitro-diphenyl-phthalide, reducing it. and 
boiling the diazo compound with water, the product is phenol- 
phthalem. Hence, the latter compound appears to be the di- 
hydroxy derivative of diphenyl-phthalide: — 




362 DI-PHENYL-METHANE, ETC. 

C 6 H 4 .NH 2 rC 6 H 4 .OH 




c , C 6 H 4 .NH 2 c I C 6 H 4 .OH 
C 6 H 4 .CO I C 6 H 4 .CO* 
1 LO 1 

Phenol-phthalein. 



The formula for phenol-phthalein may also be written 
thus : — 

C 6 H 4 . OH p C 6 H 4 rn 

C 6 H 4 .OH >C< >C0) 

the curious arrangement of the carbonyl group being simply 
the sign of the anhydride condition between carboxyl and 
hydroxy 1, of which the simplest expression is 

OTT ° 

COOH co 

This plainly is the characteristic grouping of the lactones 
(see page 166). 

There is reason to believe that when a phthalein is treated 
with a base and converted into a salt the constitution is essen- 
tially changed, the resulting salt having a quinone-like structure 
as shown thus : — 

fC 6 H 4 .OH r C 6 H 4 .OH 

p C 6 H 4 .OH C ] = C 6 H 4 = or 

C 6 H 4 .CO I C 6 H 4 .COOK 

(o 1 

Free phenol-phthalein (lactoid formula). 

= C 6 H 4 = C< C6H4 - OH 

6 4 C 6 H 4 .COOK 

Salt of phenol-phthalein (quinoid-formula). 

"Note for Student. — Although the reactions above briefly described 
may at first sight appear to be difficult to comprehend, they are in reality 
simple enough. The student is earnestly recommended not to slight them 
on account of the long names and complex formulas involved, They afford 



FLUORESCEIN. 



363 



an excellent example of the methods upon which we rely for determining 
the nature of complex substances. Notice that all appears dark until the 
well-known substance tri-phenyl-methane is obtained, which suggests that 
all the substances are derivatives of this fundamental hydrocarbon ; and 
how easily, when this conception has once been formed, the interpretation 
of all the reactions follows. 

Among the other phthaleins that deserve special mention is 
that which is formed with resorcinol. 



Fluorescein, resorcinol-phthalein, C20H12O5. — This beau- 
tiful substance is formed by heating together resorcinol and 
phthalic anhydride to 200° : — 

2 C 6 H 4 (OH) 2 4- C 8 H 4 3 = CaoHjA + 2 H 2 0. 

Its solutions in alkalies are wonderfully fluorescent. The sub- 
stance, which is sold under the name " uranin " for the purpose 
of exhibiting the phenomenon of fluorescence, is an alkaline 
salt of fluorescein. 

From the solutions of its salts fluorescein is precipitated as a 
yellow powder of the composition, C^H^O* This loses water 
readily on standing, and forms the compound, C^H^O,-,, which is 
yellowish red. The fact that the compound is colored has led 
to the belief that it has the quinoid structure in the free con- 
ditions as well as in its salts. 

The reaction that takes place between resorcinol and phthalic 
anhydride, when fluorescein is formed, is of the same kind as 
that which takes place between phenol and fche anhydride to 



form phenol-phthalein. We should 
thai, fluorescein has the formula : — 



therefore expect to find 



1 



C 6 H; 


( Oil 

1 on 


<\;1I. 


1 o\\ 
X 011 


C 8 H 


.CO 





I 



0, ; 11 



on 
on 

/0\\ 
C 6 H3=0 

0,11,00011 



364 



DI-PHENTL-METHANE, ETC. 



which shows its analogy to phenol-phthalein, 

C 6 H 4 .OH 

C 



C 6 H 4 .OH 
C 6 H 4 .CO 

1 



It is found, however, that in reality fluorescein corresponds to 
the above formula less one molecule of water ; and it is believed 
that the water is given off as represented thus : — 

OH 



C 6 H 3 { 
C 6 H 3 



roH 
o 

[OH 
C 6 H 4 .CO 

— i 

Fluorescein. 



or C 



C 6 H 3 < 







= C 6 H 3 =0 
C 6 H 4 .COOH 



Bosin, tetra-brom-fluorescem, C2oHsBr405, is formed by 
treating fluorescein with bromine. Its dilute solutions have 
an exquisite, delicate pink color which suggests a color often 
seen in the sky at the dawn of day. Hence the name eosin, 
from 7/us, dawn. It is fluorescent, and is used as a dye. 



CHAPTER XVII. 
HYDROCARBONS, CnH 2n -8, AND DERIVATIVES. 

The hydrocarbons thus far considered are of three classes. 
They are: (1) paraffins, or saturated hydrocarbons of the 
marsh-gas series ; (2) unsaturated hydrocarbons related to 
the paraffins ; and (3) hydrocarbons which contain residues 
of the saturated paraffins and of benzene. 

We now pass to a brief consideration of a hydrocarbon which 
is made up of a residue of benzene and of an unsaturated par- 
affin. It bears to ethylene the same relation that toluene bears 
to marsh gas ; that is to say, it is phenyl-ethylene. 

Styrene, phenyl-ethylene, CsHsCCgHs . CH . OH2). — This 
hydrocarbon is contained in liquid storax, — a fragrant, honey- 
like substance which exudes from various plants, as the liquid- 
amber and in coal-tar xylenes. It is formed by distilling 
cinnamic acid with lime : — 

C 9 H 8 2 =C 8 H 8 + OCX- 
Note fok Student. — What does this reaction suggest with regard 
to the relation between cinnamic acid and styrene? 

It is also formed from phenyl -ethane, („II,.(YII„ in the same 
vvny that ethylene is formed from ethane : — 

J C 2 H 6 + Hr, = C,H,r>r + HBr 

ICaHjBr 4- KOII = (Ml, + KBr + H,0 J 

C (? H,.C,H 5 + Br, = (\,II,.(\,U ( Ur + HBr; 

C 6 H,.C,Il 4 Br + KOII .-= C, ; ll,.l MI, | KBr + I1 : 0. 

Styrene. 



366 HYDROCARBONS, C n H 2n _ 8 , AND DERIVATIVES. 

Its formation by heating acetylene was mentioned on p. 
242: — 

4 C 2 H 2 = C 8 H 8 . 

Note for Student. — What other polymeric product is obtained by 
heating acetylene ? 

Styrene is a liquid of an aromatic odor ; boils at 140° : 
insoluble in water; miscible with ether and alcohol in all 
proportions. 

When heated alone up to 300°, or even when allowed to stand 
at ordinary temperatures, it is converted into a polymeric modi- 
fication called meta-styrene, which is a solid. This same change 
is readily effected by several reagents, such as iodine and con- 
centrated sulphuric acid. Styrene unites directly with chlorine 
and bromine in the same way that ethylene does (see p. 227) : — 

C 6 H 5 . CH : CH 2 + 2 Br = C 6 H 5 . CHBr . CH 2 Br. 

It unites with hydrobromic acid, forming phenyl-ethyl 
bromide : — 

C 6 H 5 . CH : CH 2 + HBr = C 6 H 5 . CH 2 . CH 2 Br. 

Hydriodic acid reduces it to phenyl-ethane : — 

C 6 H 5 . CH : CH 2 + 2 HI = C 6 H 5 . CH 2 . CH 3 + 2 I. 

Chromic acid and other oxidizing agents convert styrene into 
benzoic acid (see remarks, p. 265). Some higher members of 
this series have been prepared, such as phenyl-propylene, plienyl- 
butylene, etc. ; but at present they are not of sufficient impor- 
tance to make their consideration necessary. 

Styrene is closely related to cinnamic acid, from which the 
interesting and important compounds of the indigo group are 
obtained. 

Styryl alcohol, C 9 HioO(C 5 H6 . CH : CH . CH 2 OH) . — This 
alcohol occurs in nature in the form of an ethereal salt of 
cinnamic acid in liquid storax, and also in balsam of Peru. 
It forms long, thin needles, which melt at 33°. It boils 



CINNAMIC ACID. 367 

at 250°. It takes up hydrogen, and yields phenyl-propyl al- 
cohol, C 6 H 5 . CH 2 . CH 2 . CH 2 OH (see p. 312) : — 

C 6 H 5 . CH : CH . CH 2 OH + H 2 = C 6 H 5 . CH 2 . CH 2 . CH 2 OH. 

By treatment with hydriodic acid it yields allyl-benzene 
(phenyl-propylene), C 6 H 5 . CH : CH . CH 3 , and toluene. 

When oxidized with platinum "black it is converted into the 
corresponding aldehyde, cinnamic aldehyde; and, by further 
oxidation, into cinnamic acid. The relations between the three 
substances are the familiar ones of a primary alcohol, and the 
corresponding aldehyde and acid : — 

C 6 H 5 . CH : CH . CH 2 OH. C 6 H 5 . CH : CH . CHO. 

Styryl alcohol. Cinnamic aldehyde. 

C 6 H 5 .CH:CH.C0 2 H. 

Cinnamic acid. 

These compounds are the /^-phenyl derivatives of allyl alcohol, 
acrolein, and acrylic acid : — 

CH 2 : CH . CH 2 OH. CH 2 : CH . CHO. CH 2 : CH . COoH. 

Allyl alcohol. Acrolein or Acrylic arid. 

acrylic aldehyde. 

P^enSrync' acid, I 0*0,(0* . CH : CH . CO,H) . 

Cinnamic acid is found in liquid storax, partly in the free con- 
dition, and partly in the form of an ethereal salt in combination 
with styryl alcohol, as styryl cinnamate, in the balsams of Tolu 
and Peru. It can be made synthetically : — 

1. By heating together benzoic aldehyde and acetyl chlo- 
ride : — 

(\;II,.C01I +CH 8 .COCl = C e H a .C 8 H a .C0 2 H i HC1. 

This reaction will be better understood by writing it in two 
equations : — 

(1) C e H 8 .CH;6! + CiH2!H.COC] :C e H a .CH:CH.COCl+H 8 0; 

Ointutnvi chloride 

(2) C 6 H 8 .CH:CH.COC] + 11,0 = C e H 5 . CH : CH . COjH \ HC1. 

Cinuamyl chloride. 



368 HYDROCARBONS, C n H 2n _ 8 , AND DERIVATIVES. 

The kind of action represented in equation (1) is not un- 
common. We have already met with it in the formation of 
mesitylene from acetone (see p. 265), in which case two hydro- 
gens from each of three methyl groups unite with an oxygen 
atom from each of the three carbonyl groups. The product is 
called a condensation-product, and the action is known as con- 
densation. It has already been referred to under the head of 
cddol condensation (see p. 188). 

2. By heating together benzoic aldehyde, sodium acetate, and 
acetic anhydride. The first reaction is that of addition : — 

H H 

C 6 H 5 . C = + HCH 2 . C0 2 Na = C 6 H 5 = C - OH. 

CH 2 .C0 2 Na 

The acetic anhydride acts as a dehydrating agent and con- 
verts the product first formed into sodium cinnamate : — 

H 
C 6 H 5 . C - OH = c ^ CH . CH COaNa + -^q 

CH 2 .C0 2 Na 

3. By treating benzal chloride with sodium acetate : — 
C 6 H 5 .CH;Cl 2 ;+C;HiiH. C0 2 Na = C 6 H 5 . CH : CH. C0 2 Na+2HCl. 
C 6 H 5 .CH:CH.C0 2 Na + HCl = C 6 H 5 . CH:CH.C0 2 H + NaCl. 

The acid is now manufactured on the large scale by the last 
method. 

Cinnamic acid is a solid which crystallizes in monoclinic 
prisms. It melts at 133°, and boils at 300° to 304°. It is 
easily decomposed into styrene and carbon dioxide : — 
C 6 H 3 . CH : CH . C0 2 H = C 6 H 5 . CH : CH 2 + C0 2 . 

Oxidizing agents convert it first into benzoic aldehyde and 
then into benzoic acid. Nascent hydrogen converts it into 
hydro-cinnamic or phenyl-propionic acid, C 6 H 5 . CH 2 . CH 2 . C0 2 H 
(p. 326). It unites with hydrochloric, hydrobromic, and hydri- 
odic acids : — 



COUMARIN. 369 

C 6 H 5 . C 2 H 2 . C0 2 H + HC1 = C 6 H 5 . C 2 H 3 C1 . C0 2 H. 

Phenyl-chlor-propionic acid. 

Bromine yields the addition-product C 6 H 5 . C 2 H 2 Br 2 . C0 2 H. 
Treated with substituting agents, such as nitric acid, etc., it 
yields substitution-products in which the entering atoms or 
groups are contained in the benzene residue, in the ortho and 
para positions relatively to the acrylic acid residue, C 2 H 2 .C0 2 H. 

Nitro-cinnamic acids, C 6 H 4 { S 2 ;? 2 • C ° 2H . — The ortho- 

and para-acids are formed by dissolving cinnamic acid in nitric 
acid. 

Note for Student. — What are the products when toluene is treated 
with nitric acid ? When benzoic acid is treated in the same way ? To 
which case is the above analogous ? 

Amino-cinnamic acids, C0H4 i ri™ ' ^ W2 . — These acids 

^ NH2 

are formed by treating the nitro-acids with reducing agents. 
The ortho-acid loses water when set free from its salts, and forms 

/ CII = CH .011 = 011 

the anhydride carbostyril, C C H4\ I or C 11 ( ^ I > 

\NII-CO \ N = C(OH) 

analogous to hydro-carbostyril (p. 32(>). 



Coumarin, C«.»Hi-,0-j( C0H1 ^ ] j J, is a compound found 

in Tonka beans, and in many other plant substances. It IS 
made synthetically from salicylic aldehyde, sodium acetate, ami 
acetic anhydride, just as cinnamic acid is made from benzoic 
aldehyde, sodium acetate, ami acetic anhydride. The first 
product of this action is probably ortho-hydroxy-cinnamic acid, 

or coumaric acid, c\,ll 4 ^ 4 ... , which then loses water. 

yielding the anhydride or coumarin. Coumarin has a pleasant 
odor. Like that of sweet clover, and is used in perfumery. In 
wry great dilution it has the odor oi' new-mown hay. Treated 

with bases, it yields salts o( coumaric acid. 



(1) 


C 2 H 4 


(2) 


C 2 H 4 Br 2 




C 6 H 5 . C 2 H 3 




C 6 H 5 . C 2 H 3 Br 2 



CHAPTER XVIII. 

PHENYL-ACETYLENE AND DERIVATIVES. 

Phenyl-acetylene, acetenyl-benzene, CeHs.C-CH, bears 
to acetylene the same relation that styrene, or phenyl-ethylene, 
bears to ethylene. It is made from styrene in the same way 
that acetylene is made from ethylene : — 

+ Br 2 = C 2 H 4 Br 2 ; 

+ 2 KOH = C 2 H 2 + 2 KBr + 2 H 2 0. 

+ Br 2 = C 6 H 5 .C 2 H 3 Br 2 ; 

+ 2 KOH = C 6 H 5 . C 2 H + 2 KBr + 2 H 2 0. 

Phenyl-acetylene. 

It is a liquid that boils at 139° to 140°. It unites directly 
with four atoms of bromine, forms metallic derivatives, and, in 
general, conducts itself like acetylene (which see). 

Phenyl-propiolic acid, CgHeO^C^Hs.C : C.CO2H).— This 
acid is a carboxyl derivative of phenyl-acetylene, bearing to it 
the same relation that cinnamic acid bears to phenyl-ethylene. 
It is made from cinnamic acid, by treating the dibromine addi- 
tion-product with alcoholic potash. The reaction takes place 
in two stages : — 
C 6 H 5 . CHBr . CHBr . C0 2 H = C 6 H 5 . CH : CBr . C0 2 H + HBr ; 
C 6 H 5 . CH : CBr . C0 2 H = C 6 H 5 . C • C . C0 2 H + HBr. 

It forms long needles, which melt at 136° to 137°. When 
heated with water 120°, it breaks up into carbon dioxide and 
phenyl-ac etylene. 

Ortho-nitro-phenyl-propiolic acid, CeH4 < Z?~ , is 

<■ JNO2(0) 

made from the dibromide of ortho-nitro-cinnamic acid, in the 
same way that phenyl-propiolic acid is made from the dibromide 



INDIGO-BLUE. 371 

of cinnamic acid (see preceding paragraph). It is of special 
interest, for the reason that it can easily be transformed 
into indigo. The transformation is most readily effected by 
boiling it with alkalies and grape sugar, or some other mild 
reducing-agent. The reaction is represented by the following 
equation : — 

2 C e H 4 1 w> C ° 2H + H 4 = C 16 H 10 N 2 O 2 + 2 C0 2 + 2 H 2 0. 

( 1N ^2(0) lndig0 . 

Ortho-nitro-phenyl- 
propiolic acid. 

Indigo and Allied Compounds. 

• 
In several plants, Indigofera tinctoria, Isatis tinctona, etc., 

there occurs a glucoside called indican, which, under the influ- 
ence of dilute mineral acids and certain ferments, breaks up, 
yielding indigo-blue and a substance belonging to the glucose 
group. The indigo of commerce is prepared in the East and 
West Indies, in South America, Egypt, and other warm countries. 
At the proper stage the plants are cut off down to the ground, 
put in a large tank, and covered with water. Fermentation 
takes place, the indican breaking up and yielding indigo, as 
above stated. The liquid becomes green, and then blue. 
When the fermentation is finished, the liquid is drawn off 
into a second tank. This liquid contains the coloring-matter 
in solution. In contact with the air it is oxidized, forming 
indigo, which, being insoluble, is thrown down. In order to 
facilitate the precipitation of the indigo, the Liquid is thoroughly 
stirred. Finally, the liquid is drawn o\'[\ the precipitated indigo 
pressed and dried, and then sent into the market 

The substance prepared as above has a dark-blue color, and 
contains other coloring-matters besides indigo-blue. Its value 
depends upon the amount o\' the definite compound, indigo-blne. 
contained in it, 

Indigo-blue, indigrotin, OieHioNsOa. — Indigo-blne is ob- 
tained from commercial indigo by reducing it to iudisro-white, 



372 PHENYL-ACETYLENE AND DERIVATIVES. 

and then exposing the clear colorless solution to the air, when 
indigo-blue is precipitated. 

Experiment 79. Into a test-tube put a small quantity of powdered 
indigo ; add fine zinc filings or zinc dust and caustic soda. When the 
mixture is heated the indigo forms a colorless solution. When this 
result has been reached, pour some of the solution into a small evapo- 
rating-dish. Contact with the air colors it blue. 

Indigo-blue can be made artificially by a number of methods, 
among which the two following are the principal ones : — 

1. By boiling ortho-nitro-phenyl-propiolic acid (which see) 
with an alkali and grape sugar. 

2. From ortho-amino-benzoic (anthranilic) acid by treating 
it with chlor-acetic acid and fusing the product thus obtained 
with caustic potash : — 



NH 2 . _ TT _„ „„ NH.CH,.C0 2 H 

+ HC1 



(1) C 6 H 4 < + C1CH 2 . C0 2 H = C 6 H 4 < 



(2) C 6 H 4 <^ H - COOH = C 6 H 4 <*J>CH.COOH 

+ H 2 0; 

^ mr nnnir 

CO 



(3) 2C 6 H 4 <^>CH.COOH 



NH NH 

CO >C ' G< CO 



= C 6 H 4 <" >C:C<" >C 6 H 4 + 2C0 2 + 2H 2 . 



The later method is now used on the large scale very successfully. 
The anthranilic acid is prepared from phthalic acid, which is 
prepared from naphthalene by oxidizing it with concentrated 
sulphuric acid in the presence of a little mercury. The history 
of the attempts to prepare indigo synthetically is full of in- 
terest. At present the artificially prepared product is driving 
natural indigo out of the market. 

Indigo-blue crystallizes from aniline in dark-blue crystals. 
It sublimes in rhombic crystals. Its vapor has a purple-red 
color. It is insoluble in water, alcohol, and ether; soluble in 



INDIGO-WHITE. 373 

aniline and chloroform. Oxidizing agents convert it into isa- 
tine (which see). Heated with solid caustic potash, it yields 
carbon dioxide and aniline ; boiled with a solution of caustic 
potash and finely-powdered black oxide of manganese, it is 
converted into ortho-amino-benzoic acid (anthranilic acid) (see 
p. 321). 

Indigo-white, C16H12N2O2, is formed by reduction of indigo- 
blue, as above described. Its solutions rapidly turn blue in the 
air, in consequence of the formation of indigo-blue. 

When indigo is oxidized with nitric acid, isatine, C 8 H 5 N0 2 , 
is formed : — 

C 16 H 10 N 2 O 2 + O 2 =2C 8 H 5 NO 2 . 

When isatine is treated with sodium amalgam, it takes up 
hydrogen, and yields dioxindol, C 8 H 7 lSr0 2 : — 

C 8 H 5 N0 2 + H 2 = C 8 H 7 N0 2 . 

Isatine. Dioxindol. 

By further reduction, dioxindol loses an atom of oxygen, yield- 
ing oxhidol, C 8 H 7 NO : — 

C 8 H 7 N0 2 +H, = C 8 H 7 NO + HoO. 

Dioxindol. Oxlndol. 

The constitution of indigo is deduced from a consideration 
of a number of facts. In the first place, its vapor density 
shows that it has the molecular weight represented by the 

formula CL.1 1 10 N .,().,. 

10 IU - - ^^ 

Its relations to isatine, C e H 4 < >CO, make it probable 
that indigo contains two groups, CeH 4 <-^>C=, united. It 
can be made, for example, by reducing isatine chloride, 
<\ ; II,<^ ^CCl, a reaction that- can bo most readily inter- 
preted thus : — 
11 / C °\ ( vi+.l H-C 11 / r0 V • C C0 V 11 -4-2HC1 



374 PHENYL-ACETYLENE AND DERIVATIVES. 

Further, indigo can be made from di-o-nitro-di-acetylene, 

n — n n — q 

C 6 H 4 < ~~ ~~ > G 6 H 4 , a fact that shows that the union 

between the two halves of the indigo molecule is between car- 
bon atoms. The presence of two imino groups is shown by 
introducing radicals, and then decomposing the ethers thus 
formed. It is found that the radicals are given off in combina- 
tion with nitrogen in the form of substituted ammonias. 

All these facts, and all others that have been established by 
the investigations on indigo, are in harmony with the view 
expressed by the formula for indigo already given : ■ — 

0ft<~>O:O<~>Q^ 



CHAPTER XIX. 

HYDROCARBONS CONTAINING TWO BENZENE 
RESIDUES IN DIRECT COMBINATION. 

Just as the marsh-gas residue, methyl, CH 3 , unites with methyl 

CH 3 
to form ethane, I , so the benzene residue, phenyl, C 6 H 5 , 

CH3 C 6 H 5 

unites with phenyl to form the hydrocarbon, diphenyl, i , and 

CeH 5 

residues of toluene and of the higher members of the series 

unite in a similar way to form homologues of diphenyl. 

Diphenyl, CisHioCCoHs.CgH.O. — This hydrocarbon is made 
by treating brom-benzene with sodium : — 

2 C 6 H 5 Br -J- 2 Na = C 12 H 10 + 2 NaBr ; 

and by conducting benzene through a tube heated to redness : — 

206^ = 0^1^0 + ^ 

It forms large, lustrous plates. It, molts at 70.5°, and boils 
at 254°. It is easily soluble in hot alcohol and ether. 

Diphenyl is an extremely stable substance. It resists the 
action of ordinary oxidizing agents, but. with strong ones it 
yields benzoic acid. A large number o\' derivatives o( diphenyl 
have been studied. 

Substitution products of diphenyl. — Substituting agents as 
bhe halogens, nitric ami sulphuric acids, act upon diphenyl 
much in the same way as they do upon toluene, Of the mono- 
substitution products, three varieties, ortho, meta, :uni para, 
;ire possible. ()t' those tin 1 para derivatives are most < 



376 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

obtained by the direct action. At the same time ortho deriva- 
tives are formed to some extent. By further action ortho-para 
products and di-para products are formed. In the latter the 
substituting atoms or groups occupy the positions indicated 
below : — 

H H ■ H H 

c c c c 



XC <Z>-<Z> 

c c c c 

H H H H 



cx 



C6H4 . NH2( P ) 
Benzidine, I . — This is dipara-diamino-diphenyl. 

C6H4 . NH2( ? ) 
It is formed by reduction of dinitro-diphenyl, and also by the 
reduction of azobenzene in acid solution. In the latter case 
hydrazobenzene, which is isomeric with benzidine, is first 
formed, and this is then transformed into benzidine in the 
presence of acids (see hydrazobenzene) : — 

C 6 H 5 .NH C 6 H 4 .NH 2 

C 6 H 5 .NH C 6 H 4 .NH 2 

Hydrazobenzene. Benzidine. 

Benzidine is manufactured on the large scale by this method. 
It is a solid that melts at 122°. 

The amino groups are in the two para positions in benzidine. 

Benzidine dyes. — Benzidine, being an amino derivative of an 
aromatic hydrocarbon, is readily diazotized, and the final prod- 
uct of the action of nitrous acid is a compound containing two 
diazo groups or a tetrazo compound. Thus the chloride gives 
a tetrazo chloride : — 

C 6 H 4 . NH 2 . HC1 C 6 H 4 . N 2 C1 

C 6 H 4 .NH 2 .HC1 C 6 H 4 .N 3 C1 



NAPHTHALENE. 377 

The tetrazo compound reacts with great ease with aromatic 
amino-sulphonic acids, hydroxy-acids, and phenol-sulphonic 
acids, forming valuable dyes that have the power to unite 
directly with cotton. They are called substantive dyes. The 
'first dye of this kind that came into use was known as Congo 
red. This is made by treating diphenyltetrazonium chloride 
with sodium naphthionate. Naphthionic acid, as will be shown 
further on, is a derivative of naphthalene (which see). 

Ghrysamin is made by the action of sodium salicylate on 
diphenyltetrazonium chloride : — 

nu ™- ri C 6 H 4 < OH C 6 H 4 .N 2 .C 6 H 3 < OH 

6 H 4 .JN 2 U 6 ^gQ^ 6 4 2 6 3^ CQsNa 

+ _ TT = ___ +2HC1. 

C 6 H 4 .N 2 C1 C 6 H 4 <OH 6 6 H 4 .N 2 .C 6 H 3 <OH 

C0 2 Na COoNa 

C(>H4\. 
Carbazol, I )NH, is a curious derivative of diphenyl 

that is found in coal tar in small quantity. It has been shown 
to be a substituted ammonia containing a residue of diphenyl. 
It is properly designated by the name diphenyl-imide, and is 

C G H4 

represented by the formula 1 >N1I. It has been made syu- 
thetically by passing the vapor of diphenyl amine, Nii-jV B , 

through a red-hot tube, a reaction taking place which is analogous 
to that mentioned above as taking place when benzene is treated 
in the same way, the product in the latter ease being diphenyl. 

Naphthalene, CioHs. — While the relations o\' diphenyl to 
benzene arc 1 clearly shown by its simple synthesis from brom- 
benzene, the relations o\' napthalene to benzene have been 
discovered through a careful study of its chemical conduct 
The facts can be best interpreted by assuming that the mole- 
cule of naphthalene is formed by the anion o( two benzene 
residues in such a way that they have two carbon atoms in 
common, as represented in the formulas 



378 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

H H 

HC-CH-C-CH-CH H(7 XT T)H 

I I I and | II I • 

HC-CH-C-CH-CH HC^ /C^ ^CH 

c 
H H 

How this conception was reached will be shown below, after 
the properties and the reactions of naphthalene shall have been 
discussed. 

Naphthalene is a frequent product of the heating of organic 
substances. Thus, it is formed by passing the vapors of alco- 
hol, ether, acetic acid, volatile oils, petroleum, benzene, toluene, 
etc., through red-hot tubes ; and, also, by treating ethylene and 
acetylene in the same way. It is therefore found in coal tar, 
and in gas-pipes used for gas made by heating naphtha, 
gasoline, etc., to high temperatures. It has been made 
synthetically : — 

1. By treating o-xylylene bromide with the sodium com- 
pound of ethyl acetylene-tetra-carbonate ; saponifying the ester 
thus formed; and distilling the silver salt of the resulting 
acid : — 

H 

C CH 2 Br 

Hc/^c/ NaC (C0 9 C 2 H 5 ) 9 

+ I 

HCl XL NaC(C0 2 C 2 H 5 ) 2 

C CH 2 Br 

H 

H 

C CH 2 

nc/^°y / \c(co 2 c 2 R 5 ) 2 



HC W 

c c 
H H 2 



+ 2 NaBr, 

C(COoC 2 H 5 ) 2 



S* v 



NAPHTHALENE. 



379 



<CH 2 — C(C0 2 C 2 H 5 ) 2 
I 
CH 2 -C(C0 2 C 2 H 5 ) 2 



^C 6 H 4 



/ 



CH 2 -C(C0 2 H) 2 
•CH 2 -C(C0 2 H) 2 



CH-CH 
^■C 6 H 4 <( | 

\CH~CH 



/ 



2. By conducting phenyl-butylene bromide over heated 
lime : — 

/CH-CH 
C G H 5 . CH 2 . CH 2 . CHBr . CH 2 Br — >- C 6 H 4 < | . 

\CH-CH 

3. When pheny lisocrotonic acid, C G H 5 . CH = CH . CH 2 . COOH, 
is heated, it loses water and gives a-naphthol, a hydroxyl de- 
rivative of naphthalene : — 



H 
C 



II 
C 



HC 



V^C S 
C H CO 



CH 
CH 



H 



OH 



H H 

c c 



HC 



c c 

H OH 



CH 



By reduction with zinc dust a-naphthol gives naphtha- 
lene. 

The above syntheses give a clew bo the constitution of naph- 
thalene, but they do not clear it up entirely. A study of the 
chemical conduct of naphthalene has, however, Led to a solution 
of the problem. 

Napthalone is prepared on the large scale from those por- 
tions of coal tar which boil between L80° to '1^0'\ This material 
is treated with caustic soda, ami then with sulphuric acid, and 
distilled with water vapor. 



380 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

It forms colorless, lustrous, monoclinic plates. It melts at 
80°, and boils at 218°. It has a pleasant odor; is volatile 
with water vapor, and sublimes readily. It is insoluble in 
water; easily soluble in boiling alcohol, from which it can 
be crystallized. Oxidizing agents convert it into phthalic 
acid (see Exp. 74). On the large scale phthalic acid is 
made from it by oxidizing with sulphuric acid, as has 
already been stated. It is used as an antiseptic and in- 
secticide. The well-known moth balls, for example, are made 
of naphthalene. 

The ease with which naphthalene yields phthalic acid, sug- 
gests that the hydrocarbon is probably a di-derivative of benzene 
containing two hydrocarbon residues ; such, for example, as is 

represented by the formula C 6 H 4 1 2 2 - Such a substance, how- 
ever, contains unsaturated paraffin residues, and hence ought 
readily to take up bromine, hydrobromic acid, etc. Bromine 
and chlorine are indeed taken up easily, but the products 
thus obtained act rather like the addition-products of benzene 
than the addition-products of the unsaturated paraffins. They 
break up readily, and yield stable substitution-products of 
naphthalene. 

We have seen that a hydrocarbon containing a benzene 
residue and an unsaturated paraffin residue, as, for example, 
styrene or phenyl-ethylene, C 6 H 5 . C 2 H 3 , and phenyl-acetylene, 
C 6 H 5 . C 2 H, when treated with bromine or hydrobromic acid, 
takes them up as readily as ethylene and acetylene, and this 
action takes place before substitution. According to this, 
naphthalene ought to take up bromine and especially hydro- 
bromic acid with avidity before substitution of its hydrogen 
takes place. 

While it does take up four atoms of chlorine or of bromine, 
it does not take hydrochloric or hydrobromic acid, a fact that 
makes it improbable that naphthalene contains unsaturated 
paraffin residues 



NAPHTHALENE. 381 

The formula C 6 H 4 < 2 T 2 and similar ones being thus rendered 

I C 2 H 2 

extremely improbable, the next thought that suggests itself is 
that the two groups C 2 H 2 may be united, as represented in the 

i (CH.CH 
formula C 6 H 4 ) I . Assuming, further, that the two groups 

^CH.CH 

are united to two carbon atoms of the benzene residue which 
are in the ortho relation to each other, we may write this same 
formula thus : — 

H 

HC X X C-CH-CH 

I I I 

HCv /C-CH-CH 
H 

or, what is the same thing, — 

H H 

HCT X C X X CH 

I ! I 

x c c 

H IT 

This formula represents naphthalene :is made up of two 
benzene residues united in such a way that they have two 
carbon atoms in common. This, as has been stated, repre- 
sents the hypothesis at present held in regard to the nature o( 
naphthalene. 

As regards the assumption that the two residues are united 
through carbon atoms which are in the ortho position relatively 
to each other, it. should be said that this assumption is made 
because phthalio acid is the product oi oxidation ; and the facts 
already considered have shown us that terephthalie aeid must 
be represented by the formula 



382 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

C0 2 H 

HC X X CH 

I I 

X CT 



C0 2 H 



and isophthalic acid by 



C0 2 H 

HC X X CH 

I I 

HCx /CC0 2 H 

H 

and hence, in terms of the accepted hypothesis, the third pos- 
sible formula must be given to phthalic acid ; viz., — 

H 

HC X x C.C0 2 H 

I I 

HC X /C.C0 2 H 

H 

Are there any facts besides those above mentioned which 
make the hypothesis appear probable ? 

By a different line of reasoning, based upon other facts, the 
conclusion is reached that naphthalene is made up of two ben- 
zene residues which have two carbon atoms in common, and the 
only formula which represents this conception is the one already 
given. The facts which lead to this conclusion are the fol- 
lowing : — 

When nitro-naphthalene is oxidized it yields nitro -phthalic 
acid. This shows that the nitro group is contained in a 
benzene residue ; and we may represent it by the formula 



NAPHTHALENE. 



383 



C 6 H 3 .N0 2 J ~ „ , the oxidation taking place as indicated thus : 
( C2H2 

C 6 H 3 . NO, J ^ +90 = C 6 H 3 . N0 2 1 °° 2 J + H 2 + 2 CO, 



By reducing this same nitro-naphthalene, amino-naphthalene 
is obtained; and, when this is oxidized, phthalic acid is 
formed : — 

C 2 H . NIL, 

C 2 H 2 



C 6 H 4 j 



2 + 12 = C 6 H 4 



rco 2 H 

JC0 2 H 



+ 2C0 2 + HN0 3 + H 2 0. 



These two reactions show (1) that the part of nitro-naphtha- 
lene in which the nitro group is situated is a benzene residue ; 
(2) that there is another benzene residue in the compound into 
which the nitro group has not entered. 

These transformations may be represented thus : — 





H H 






HC 


/\ C /\ 


CH 


HC 


VcV 




CH 


H 


N0 2 


Nitro-naphthalene. 


H H 


C C 


HO 


/^/\ 


CH 


HC 


\/cK/ 

n ^ n 


CH 


H T 


Nil, 


/ 


.mino-naphti 


alone 



H 

C 

HC,/ 



> 



CH 



C0 2 H 
C0 9 H 



C 

NO, 

Nitro-phthalic acid. 



II 

C 



c/V- 



II 



A 
C 

11 

Phthalto acid. 



COM 



COM 



It has been noticed, also, that by oxidation of a naphthalene- 
sulphonic acid, both sulpho-phthalio and phthalic aoid itself 

are obtained. 



384 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

It follows, from these facts, that naphthalene is made up of 
two benzene residues, and the only way in which a hydrocarbon 
of the formula C 10 H 8 can be thus made up, is by having two 
carbon atoms common to the two residues, as represented in 
the formula already given : — 

H H 

HC/ \c/ \CH 

I I I 

HCv. /C\ /CH 

x <r x c x 

H H 

The proof just given for this formula is independent of any 
notions regarding the ortho, meta, and para relations in ben- 
zene. As phthalic acid is the product of oxidation, it follows 
that the carboxyl groups in the acid must bear to each other 
the relation expressed by the formula 

H 

HC/ \c-C0 2 H 

I I 

H 

and, therefore, that in all ortho compounds the substituting 
groups bear this same relation to each other. Hence, by start- 
ing with the notion that the above formula represents phthalic 
acid, — and to this notion, it must be remembered, we are led 
independently of any facts connected with the formation of the 
acid from naphthalene, — the accepted formula of naphthalene 
follows naturally. 

Derivatives of Naphthalene. 

An interesting fact that has been discovered by a study of the 
mono-substitution products of naphthalene is this, — that two, 
and only two, varieties can be obtained. There is an a- and 



DERIVATIVES OF NAPHTHALENE. 385 

a /5-chlor-naphthalene, an a- and a /3-brom-naphthalene, etc., 
etc. This fact is quite in harmony with the views held 
regarding the constitution of naphthalene, as will readily be 
seen by examining the formula somewhat more in detail 
We see that there are two, and only two, kinds of relations 
which the hydrogen atoms bear to the molecule ; all those 
marked with an a being of one kind, and all those marked 
with a p being of another kind: — 

aH aH 

! I I 

aH aH 

Here, again, a problem presents itself like that of the di- 
substitution products of benzene. The theory gave us three 
formulas, and three compounds are known. The problem was, 
to determine which formula to assign to each compound. Here 
we have two formulas for two brom-naphthalenes and other 
mono-substitution products of naphthalene, and we actually 
have two compounds; and the question arises, which of the 
two formulas must we assign to a given compound ? The 
method adopted is simple, and can be explained in a few words. 
That nitro derivative of naphthalene which is known as a-nitro- 
naphthalene yields nitro-phthalic acid by oxidation; and the 
relation of the nitro group to the carboxyl groups, in this acid, 
has been determined. It is expressed by the formula 

NO, 

nr/ \c-COaH 

I I 

ik\ /r-aui 

H 

Formula l 



386 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

while the formula of the other nitro-phthalic acid is 

H 

N0 2 c/ \c-C0 2 H 

HC V /C-C0 2 H 

H 

Formula II. 

As a-nitro-naphthalene yields the acid of formula I., it fol- 
lows that in it the nitro group must occupy the position of one 
of the hydrogen atoms marked a in the above formula for naph- 
thalene. Those substitution-products of naphthalene which 
belong to the same series as a-nitro-naphthalene are called a 
derivatives. In the (3 compounds the substituting group or 
atom must occupy the place of one of the hydrogen atoms 
marked /3. 

According to the theory in every case in which the two 
substituting atoms or groups are the same, there are ten di- 
substitution products of naphthalene possible. For example, 
there are ten di-chlor-naphthalenes possible. All ten are known 
and no more. The relations between the two substituting 
atoms can be followed by the aid of the figure below : — 

1 




The numbers mark the positions of the eight hydrogen atoms 
in naphthalene. Two substituting atoms or groups may bear 
to each other the relations 

1,2; 1,3; 1,4; 1,5; 1,6; 1,7; 1,8; 2,3; 2,6; 2,7. 

Further there are fourteen tri-substitution-products possible 
in which the three substituting atoms or groups are the same. 



NAPHTHOIC. 387 

There are fourteen tri-chlor-naphthalenes possible and all are 
known. 

a-Amino-naphthalene, a-naphthylamine, a-CioH7.NH2-— 

This is formed by the reduction of a-nitro-naphthalene, which 
is the chief product of the treatment of naphthalene with nitric 
acid in the cold. It melts at 50°. It is also formed from the 
corresponding hydroxyl compound, a-naphthol, by heating it 
with the ammonia compound of zinc chloride. It turns red in 
contact with the air. It has a pungent odor. 

p-Amino-naphthalene, P-naphthylamine, P-C10H7 • NH2, 
is made from /3-naphthol by treating it with the ammonia com- 
pound, of zinc chloride. It melts at 112° and has no odor. 

Several of the sulphonic acids derived from the naphthyl- 
amines are of value for the preparation of dyes. 

Naphthionic acid, 1, 4, naphthylamine-sulphonic acid. 
— It is the sodium salt of this acid that gives Congo red when 
brought together with diphenyltetrazonium chloride (see ben- 
zidine) : — 

C 6 H 4 .N 2 Cl + C 10 H (; <^ Na 
C 6 H 4 .N 2 Cl + C 10 H 6 <^ Na 

C 6 H 4 .N 2 .C 10 H 5 <gg ra 

SO,Na 
"Nil. 



T +2HC1. 

! 6 H 4 .N,.(\ 

Congo red. 



When /3-naphthylamine is treated with sulphuric arid, four 
mono-sulphonic acids are formed. 

Naphthols, C10H7.OH. — Both o\' the uaphthols occur in 
coal tar. Tlu\y act in general like the phenols, though the 
hydroxyl group reacts more readily than that in the phenols. 
It lias already foeeD seen that t ho ammo group can be suhsti- 



388 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

tuted for the hydroxyl group of the naphthols. The naphthols 
are made by fusing the corresponding sulphonic acids with 
caustic potash : — 

C 10 H 7 . S0 3 K + KOH = C 10 H 7 . OH + K 2 S0 3 . 

Both sulphonic acids are formed when naphthalene is treated 
with sulphuric acid. At low temperatures (80°) the a-acid is 
the chief product. At higher temperatures (160°) the /3-acid 
is formed in larger quantity. Indeed, the a-variety is converted 
into the ^-variety when heated with sulphuric acid. 

The synthesis of a-naphthol by heating phenylisocrotonic 
acid has already been referred to (see page 379). 

a-Naphthol is difficultly soluble in water, crystallizes in lus- 
trous needles, and melts at 95°. 

fi-Naphtliol is easily soluble in water, crystallizes in leaflets, 
and melts at 122°. 

Naplithol-sidphonic acids. — Many of these are known, and 
are used in the preparation of azo dyes. The 1, 4, naphthol- 
sulphonic acid is the one principally used. 

Among the azo dyes derived from naphthalene the following 
may be mentioned : — 

a-Naphtliol orange, formed by the action of a-naphthol on the 

sodium salt of benzene-diazonium sulphonate. It is represented 

u *.-u t i ^ TT ^ N 2 C 6 H 4 S03Na(4) . 

by the formula Ci H 6 < ^ b ; 

fi-NapTithol orange, made with /3-naphthol in the same way ; 

Biebrich scarlet, made from /?-naphthol by treating it with a 
diazo compound formed by first diazotizing sulphanilic acid, 
treating the diazo compound thus obtained with sulphanilic 
acid, diazotizing the product and treating with /?-naphthol. 
This dye may serve as an example of the possibilities pre- 
sented by the azo compounds. Its formula is 

N CH SOJSfa (1) 

C,oH 6 < | J 6 3 ^N 2 .C 6 H 4 .SO s Na (2)' 



/3-NAPHTHO-QUINONE. 389 

Poirrier's Orange II. is formed by treating benzene-diazonium 
sulphonate (see sulphanilic acid) with /3-naphthol. Its formula 
is r H /^.Ce^.SOsNa 

The Poncedux and Bordeaux dyes are formed by treating 1, 4, 
naphthol-sulphonic acid with diazo salts. 

Some of the simpler derivatives of naphthalene are used as 
dyes. Among these the following may be mentioned : — 

Di-nitro-naphthol, C 10 H 5 (NO 2 ) 2 OH, which is used in the form 
of the sodium salt under the name of Martins' Yellow; 

( (N0 2 ) 2 

Di-nitro-naphtholsidphonic acid, CioHj-j S0 3 H , which in the 

I OH 
form of the sodium salt is used under the name Na/phthol 
Yellow S. 

a-Naphtho-quinone, CioHcOs. — This compound is obtained 
by oxidizing naphthalene with chromic acid ; also by oxidizing 
a-amino-a-naphthol and other di-substitution products of naph- 
thalene in which the two substituting groups are in the 1, 4 
position relatively to each other. It bears to naphthalene the 
same relation that ordinary quinone bears to benzene ; that is. 
it is naphthalene in which two hydrogen atoms arc replaced 
by two oxygen atoms. 

It forms yellow needles, which melt at L25°. Like ordinary 
quinone, it is volatile with water vapor. Hydriodic acid con- 
verts it into a-hydro-naphtho-quinone : — 

C 10 H e O 2 + H a = C 10 H 6 (OH) 1 , 

Note fob Student. — Compare with the action of reducing agents on 
ordinary quinone. 

p-Naphtho-quinone, CioHeO*. — This quinone is formed by 
oxidizing /8-amino-a-naphthol with ferric chloride. It consists 
of red needles that decompose a1 L15 120°, it is inodorous and 
is not volatile. While in a-naphtho-quinone the two oxygen 
atoms are in the 1, 1 (para) position to eaoh other, as they are 



390 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

in ordinary benzoquinone (see Quinone), in /^-naphthoquinone 
the oxygen atoms are ortho to each other. a-Naphtho-quinone 
in general resembles ordinary quinone ; /?-naphtho-quinone does 
not. The formulas of the two naphtho-quinones are here 
given : — 

CH c CO CH CO 

HCi^Y^iCH HCi^V^iCO 



HC w CH HC %AJ CB - 

C u CO C b CH 

H H 

a-Naphtho-quinone. 0-Naphtho-quinone. 

Di-hydroxy-naphtho-quinone, CioH^j^P ^ 2 , is a dye 

known by the name naphtliazarin, on account of its resem- 
blance to alizarin (which see). 

Homologues of naphthalene — like methyl- and ethyl-naph- 
thalene — have been prepared, a- and ^-Methyl-naphthalene 
have been found in coal tar. 

QUINOLINE AND ANALOGOUS COMPOUNDS. 

When quinine or cinchonine is distilled with caustic potash, 
a basic substance of the formula C 9 H 7 N is formed. This is 
called quinoline. It occurs in coal tar together with an iso- 
meric substance isoquinoline, and some homologues. Among 
the compounds homologous with quinoline are the following : — 

Quinaldine, a-Methyl-quinoline .... C 10 H 9 ]Sr. 
Lepidine, y-Methyl-quinoline .... C 10 H 9 K 
Cryptidine C u H n K. 



Quinoline, C9H7N. — Quinoline is formed by the distillation 
of quinine, cinchonine, or strychnine, with caustic potash ; is 
formed from certain derivatives of benzene ; and is found in 
coal tar. 



QUINOLINE AND ANALOGOUS COMPOUNDS. 391 

1. By passing allyl-aniline over heated lead oxide : — 

C 6 H 5 . NH . CH = CH . CH 3 + 2 = C 9 H 7 N + 2 H 2 0. 

This synthesis is similar to that of naphthalene from phenyl- 
butylene (see p. 379). 

2. By heating together glycerol, aniline, nitro-benzene, and 
sulphuric acid. In this case acrolein is probably first formed 
from the glycerol by the action of the sulphuric acid : — 

CH 2 OH CH, 

I II 

CHOH=CH +2H 2 0. 

I I 

CH 2 OH CHO 

This acrolein then combines with aniline thus : — 



HC 
HC 



TT TT 

C NH 2 C N 

1° + OHC . CH=CH,= HC | 1° V H +H..O. 

LJCH " HCl/'CH CH 

CH CH HC X 

H 

The nitro-benzene now acts as an oxidizer, and removing two 
hydrogen atoms gives quinoline : — 

H 

CH N C ,N 

HcUM-" ^^ 1 -^" - 
C HC C ( CH 

H H II 

The nitro-benzene in acting as an oxidizing agent is itself 
reduced, and the aniline thus formed miters into reaction to- 
gether with the other aniline present. The whole change can 
be represented as below : — 

2C 6 h,nh, + (\ ; h,no, + ;hvjIsO,-;h\,h-n ■ 11 ho. 



392 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

3. From o-amino-cinnamic aldehyde by loss of water : — 

X CH = CH . CHO /CH = CH 

C 6 H 4 < = C 6 H 4 < I + H 2 0; 

\\H 2 \ N-CH 

CH n NH 9 CH _ N 

S\y ^/% 

HCI II ICH HC | i| | CH ±TTn 

0P TTP PIT = UP PIT + H 20» 

CH C CH CH°CH 

This simple synthesis shows very clearly the constitution of 
quinoline. It is analogous to naphthalene in a way. Just as 
the latter is made up of two benzene rings united by two com- 
mon carbon atoms, so quinoline is made up of a benzene ring 
and a pyridine ring united in the same way. This hypothesis 
is in harmony with all the facts known in regard to quinoline. 

4. Another synthesis of quinoline is effected by starting with 
hydrocarbostyril (which see). When this is treated with phos- 
phorus pentachloride it is converted into dichlor-quinoline, and 
by reduction with hydriodic acid this gives quinoline : — 

.CH, . CH, y CH = C CI /CH = CH 

C 6 H 4 < | — ^C 6 H 4 < | — ^C 6 H 4 < | • 

Nim-co \ N=CC1 \ N=CH 

Quinoline is a colorless liquid with a penetrating odor, and 
is a powerful antiseptic. It boils at 239°. Potassium per- 
manganate converts it into quinolinic acid, which is a pyridine- 
dicarbonic acid, C 5 H 3 N(C0 2 H) 2 . The formation of this acid is 
analogous to the formation of phthalic acid from naphthalene: — 

N C CH N C/COoH 

HG^Y^jCH Hc r x if / 

HCLJv^CH HC<v xl 

CH C CH CH C C ° 2H 



HC 

HO 



a-METHYL QUINOLINE. 393 



CH n CH CH n nA tt 



CH HO 



c¥<¥h cY^H 

Jt has already been pointed out that quinolinic acid gives 
pyridine when distilled with lime and that the accepted hypoth- 
esis in regard to the constitution of pyridine is based on this 
fact and the formation of quinolinic acid from quinoline (see 
pyridine). 

Quinoline forms well-characterized salts with acids. In 
these salts it acts like a mon-acid base. The number of sub- 
stitution products derivable from quinoline is large. Thus 
there are seven mono-substitution-products possible, as will be 
seen by an examination of the figure below : — 

a) 

CH C N 

(2)H</ N ,| / \ , H(o) 

CH°CH 

ID (y) 

A substituting atom or group may take the place of any one 
of the hydrogen atoms indicated by the letters u, [3. and y, and 
the numbers 1, 2, 3, 4, each of which bears a different relation 
to the nitrogen atom. According bo this there arc seven possi- 
ble mono-methyl derivatives, .1// of these are known. $o also 
there are seven possible tnono-ch lor derivatives, and all of these 
are known. 

The methyl derivatives are designated by the letters u. ft. y, 
and the numbers 1, 2, 3, L 

a-Methyl-quinoline. Quinaldine, C>H, ,CH- N N. — This 
occurs in eoal tar, and van be made by digesting aniline, 
paraldehyde, and hydrochloric acid: — 



394 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

.CH = CH 
C 6 H 5 . NH 2 + 2 C 2 H 4 = C 6 H 4 < | + 2 H 2 + H 2 ; 

\ N = C(CH 3 ) 

and by treating o-amino-benzoic aldehyde with acetone : — 



,CHO CH 3 .CH = CH 

+ I = C 6 HZ | 

\NH 2 CO-CH, \ N = C 



7-Methyl-quinoline, Lepidine, CgHeCCILON. — This occurs 
together with quinoline and quinaldine in coal tar, and it is 
formed by distilling cinchonine with caustic potash. When 
this is brought together with iso-arayl iodide an addition- 
product is formed, and when the latter is treated with caustic 
potash the substance known as cyanin is formed : — 

2 C 10 H 9 N . C 5 H n N = C 30 H 39 N 2 I + HI. 

Cyanin forms monoclinic prisms with a metallic green lustre. 

Its solution in alcohol is deep blue. This color is destroyed 

by acids and restored by alkalies. 

/ N=CH 
1-Hydroxy-quinoline, CeHsCOHx I , is formed from 

N3H-CH 

1-quinoline-sulphonic acid by fusing it with caustic potash. 

a-Hydroxy-quinoline, Carbostyril, is formed by the elimi- 
nation of water from o-amino-cinnamic acid. It has either the 
hydroxyl or the keto group in the pyridine ring : — 

CH CH CH c CH CH Q CH 

Hc/YVjH HCAACH HCi^V^CH 



Jk lco hc UU ( 



Hc Uk lco "^ hc UU co ( : hc UU c (° h )' 

CH c N OH CH ^ NH l N 

H 2 

Hydrogen addition-products of quinoline and its derivatives. — 
Quinoline, like naphthalene, takes up hydrogen quite easily. 
Tin and hydrochloric acid convert it into tetra-hydro-quinoline, 
in which the hydrogen has been added to the pyridine ring: — 



ISOQUINOLINE. 395 



c 6 h/ 



CH 2 — CH 2 

I • 

NH - CEL 



The hydrochloride of 1, hydroxy-methyl-tetra-hydro-quino- 
line, is used as a febrifuge under the name kairine. 

The sulphate of 4, niethoxy-tetra-hydro-quinoline, called 
thalline, is also used as a febrifuge. 

The final product of the addition of hydrogen to quinoline 
is deca-hydro-quinoline, C 9 H 18 N. 

CH P CH 

ch^yy 

Isoquinoline, . — A base isomeric with quino- 

CH k/iU CH 

CH ^ CH 
line is found with it in coal tar. This base, which is called 
isoquinoline, can be made by methods that show that the 
isomerism with quinoline is due to a difference in the position 
of the nitrogen atom. In it the nitrogen atom is not directly 
connected with the benzene ring, but it is in the /^-position as 
shown in the above formula. It can be made, for example, 

from the imide of an acid of the formula (\ ; II 4 < „ ^Vn 
(homophthalic acid). This imide has the formula 

,CH«-CO 



c 6 h/ I . 

Vo - NH 



By phosphorus pentachloride it. gives dichlor^soquinoline, 

/CH = CC1 
CeH 4 / i , and this when reduced by means of zinc dust 

Vp " = N .CH CH 

gives isoquinoline, c,.,ii,< i . Isoquinoline molts at 23° 

Vll =N 

and boils at 240.5°. It resembles quinoline in its genera] 

properties. 

Several alkaloids are derivatives o\' tetra-hydro-isoquinoline, 

such, for example, as papaverine, iiarcotinc, and hydrazine. 



CHAPTER XX. 

HYDROCARBONS CONTAINING TWO BENZENE 
RESIDUES INDIRECTLY COMBINED. 

Diphenyl and naphthalene have been shown to consist of two 
benzene residues in direct combination. Diphenyl-methane is 
an example of a hydrocarbon consisting of two benzene resi- 
dues in indirect combination, C 6 H 5 . CH 2 . C 6 H 5 . As diphenyl- 
methane is closely related to toluene, it was treated of in 
connection with the hydrocarbons of the benzene series. 
There are some hydrocarbons which have been shown to 
consist of two benzene residues united by means of residues 
of unsaturated paraffins. The most important of these is the 
well-known anthracene. 

Anthracene, CuHio. — Anthracene is formed under condi- 
tions similar to those which give rise to the formation of 
naphthalene, especially by heating organic substances to a 
high temperature, and is hence found in coal tar. 

It has been made synthetically from benzene derivatives by 
a number of methods : — 

1. By heating ortho-brom-benzyl bromide with sodium : — 

2 C 6 H 4 \ ^ HsBr + 4 Na = C 14 H 10 + 4 NaBr + 2H; 



Br (0) 

= C 6 H 4 1 ™ | C 6 H 4 + 4 NaBr + 2 H. 

2. By treating a mixture of benzene and acetylene tetra- 
bromide with aluminium chloride : — 



ANTHRACENE. 397 

BrCHBr y CH v 

C 6 H 6 + | + C 6 H 6 =C 6 H 4 <| >C 6 H 4 + 4HBr. 

BrCHBr XJH' 

Anthracene is prepared in large quantity from those portions 
of coal tar which boil between 340° and 360°. The distillate 
is redistilled, and that which remains in the retort after the 
temperature has reached 350° is treated with liquid sulphur 
dioxide. When pure it forms laminse, or monoclinic plates, 
which are fluorescent. It melts at 213°, and boils at 351°. 

Anthracene takes up hydrogen, forming di-hydro-antliracene, 
C I4 H 12 , and hexaJiydro-anthraceyie, C 14 H 16 . It takes up bromine 
and chlorine, forming first addition-products, and then substi- 
tution-products. 

Oxidizing agents convert anthracene into anthra-quinone, 
C 14 H 8 2 , just as they convert naphthalene into naphtha- 
quinone. 

The formation of anthracene from ortho-brom-benzyl-bro- 
mide and from benzene and acetylene tetrabromide (see above) 
furnishes strong proof in favor of the view that anthracene 
consists of two groups, C (! H 4 , united by the group, C 2 H 2 ; thus, 
C ( jH 4 .C 2 H2.C ( iH 4 . It hence appears as a diphenylene 1 deriva- 
tive of ethane, C 2 H 2 (C (i H 4 ) 2 , analogous to diphenyl-ethane, 
C 2 H 4 (C 6 H r ,) 2 . This conception may also be expressed thus : — 

a a 

H H 

I III I 

p\U\ /C-CH-Cv XUfS 

XX y XX 

II 11 

a a 

This is the formula commonly accepted for anthracene. It is 

in harmony with a large number o\' facts, and has been an 

ellieient aid in investigations on anthracene and its derivatives. 

i Phenylene-CeH* 



398 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

The Greek letters a, ft, y, show the three different positions of 
the hydrogen atoms, and indicate that there are three possible 
mono-substitution-products of anthracene. 

Anthraquinone , Ci4H 8 2 ( = CeH4 < qq > CeEu) . — Anthra- 
quinone is formed 

1. By direct oxidation of anthracene : — 

C14H10 + 3 = C 14 H 8 2 ■+■ H 2 0. 

2. By distilling calcium benzoate : — 

C6H4< H HOOC >C|iH4 = C -> H *<co >CA + 2 H '°- 

COC1 1 

3. By treating phthalyl chloride, c 6 H 4 < mrl , with benzene 

in the presence of aluminium chloride : — 

C 6 H 4 < g£Cl + Ce H 6 = C6H4 < CO > CeBt + 2 HCL 

4. By distilling calcium phthalate : — 



C6H4 rco;o >Ca 



C6H4 (;coo >Ca 



= C 6 H 4 <^>C 6 H 4 + 2CaC0 3 . 



1 It has already been pointed out that diphenyl-phthalid is also formed from phthalyl 
chloride, benzene, and aluminium chloride. Diphenyl-phthalid is isomeric with anthra- 
quinone, as shown by the formulas 

r C 6 H 5 
C(C 6 H B ). I C 6 H 5 

C 6 H 4 < co >0 or 0-j C6H4-CO 

Diphenyl-phthalid. 

and C 6 H 4 <^>C 6 H 4 

CO 

Anthraquinone. 

The formation of these two substances from phthalyl chloride shows either that phthalyl 

coci cci 

chloride itself is a mixture of two isomeric chlorides, C 6 H 4 < _. and C 6 H 4 < 2 >0, or 
that it can act in both ways, showing thus the phenomenon of tantomerism. 



ANTHRAQUINONE. 399 

Experiment 80. Dissolve 5s commercial anthracene in 220 cc hot 
glacial acetic acid. Slowly add to the boiling solution 50s chromic acid 
in 50 cc acetic acid (50 p. a). Boil for some hours. After cooling, add 
750 cc water ; filter ; wash ; dry ; and sublime. 

Anthraquinone forms rhombic crystals, melting at 285°. It 
sublimes in yellow needles ; is insoluble in water, but slightly 
soluble in alcohol and ether. It is an extremely stable com- 
pound, resisting the action of alcoholic potash and oxidizing 
agents. Melted with solid potassium hydroxide, it yields ben- 
zoic acid : — 

C 6 H 4 < °° > C 6 H 4 + 2 KOH = 2 C 6 H 5 . COOK. 
CO 

Reducing agents convert it successively into oxanthranol, 
C 14 H 10 O 2 , anthranol, C 14 H 10 O, and anthracene, C 14 H 10 . These 
changes may be represented thus : — 

C 6 H 4 < gj > C 8 H 4 + H 2 = C e H 4 < £ JJ (0H) > C 6 H 4 ; 

Oxanthranol. 

C « H 4 < nn (0H) > C « H < + H ' = °« H < < I > C 6 H 4 + H.,0 ; 

C0 CH 

Anthranol. 

CH 

C 6 H 4 <^ H) >C 6 H 4 + H 2 =C 6 H 4 < | >tyi 4 +H,0. 
CH CH 



When heated with zinc dust, it yields anthracene. A greal 
many derivatives of anthraquinone have been made. Among 
the best known are the hydroxy] derivatives, some of which 
are much-prized dyes and are manufactured in great quan- 
tities. 

The hydroxy] derivatives of anthraquinone can be made by 
melting either the bromine derivatives or the sulphonie acids 
with caustic potash. 



400 HYDBOCABBOXS WITH TWO BEXZEXE BESIDUES. 

Di-hydroxy-anthraquinone, / CuHsO^CuHeCMOH)*]. 
Alizarin is the well-known dye that was originally obtained 
from madder root. The substance found in the root is 
ruberythric acid, a glucoside of the formula C 26 H 28 14 . When 
this is treated with dilute acids or alkalies or ferments, it is 
decomposed, yielding alizarin and a glucose : — 

VAO u + 2 H 2 = C 14 H 8 4 + 2 C 6 H J2 6 . 

Alizarin. Glucose. 

It is formed by melting dichlor- or dibrom-anthraquinone or 
anthraquinone-monosulphonic acid with caustic potash : — 

C 14 H 7 2 . S0 3 K + KOH + = C 14 H 6 2 (OH) 2 + K 2 S0 3 . 

Alizarin is now manufactured from anthracene on the large scale, 
and large tracts of land that were formerly used for cultivating 
madder are now used for other purposes. 

Experiment 81. Dissolve 20s anthraquinone in a small quantity of 
fuming sulphuric acid, heating gradually to 260°. Dissolve the product 
in a litre of water. Neutralize with finely-powdered chalk ; filter. Pre- 
cipitate with a solution of sodium carbonate ; filter ; and finally evaporate 
to dryness. The salt thus obtained is impure sodium anthraquinone-mono- 
sulphonate. In an iron crucible mix 10g of the sulphonate, 40s sodium 
hydroxide, and 3s potassium chlorate, and heat for several hours at 165° 
to 175°. The formation of alizarin, during the melting, is shown by the 
dark-purple color of the mass. When a little of this is dissolved in water, 
it should form a beautiful purple-red solution. Continue the melting until 
the mass acts in this way. Dissolve the mass in f 1 to l 1 water, and acidify. 
Alizarin is thrown down in brown amorphous flakes. Filter off, dry, and 
sublime between watch-glasses. 

Alizarin forms red needles, which melt at 289°. It dissolves 
in alkalies, forming dark purple-red solutions. When heated 
with zinc dust, it yields anthracene. It was this reaction 
which gave the first clew to the nature of alizarin, and led, 
soon after, to its synthesis. 

The two hydroxyl groups in alizarin are in the a and (3 posi- 
tions in one benzene ring, as shown in the formula 



ALIZAKIN. 



401 



CH CO C(OH) 

H{/YY^(OH) 



HC 



CH 



CH C CO C CH 

The evidence in favor of this view is this : Alizarin is 
formed by heating pyrocatechol and phthalic anhydride with 
sulphuric acid. This shows that the two hydroxyl groups are 
in the ortho position with reference to each other. It is only 
necessary to show that one of the hydroxyls is in the a position 
to make the evidence complete. A second di-hydroxy-anthra- 
quinone known as quinizarin is formed from phthalic anhydride 
and hydroquinol. In quinizarin, therefore, the hydroxyl groups 
are in the para position with reference to each other, — 

CH^CO^C(OH) 



HC 

Hcl X X JCH 
CH c CO C C(OH) 
When quinizarin is oxidized, a third hydroxyl group is intro- 
duced, and purpurin, a trihydroxy-anthraquinone, is formed. 
The same is true of alizarin. It follows therefore that in 
alizarin the hydroxyl groups are in the a and /3 positions : — 

CH c CO c C(OH) 




HC 
HC 



/Y/Y/\ 



C(OII) 
CH 



H CO C CJ 



CH CO ,C(OH) 

hc/N/N/Nch 



IK, 11 JCH 
CH C CO C G(OH) 



c CO c C(OH) 




402 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

There are ten possible di-hydroxy-anthraquinones. Nine of 
these are known. Those in which the hydroxyl groups are in 
the ortho relation to each other have coloring power. 

Purpurin, }Oi4H.O. = [OnH.O.(OH),]. 

Tri-hydroxy-anthraqumone, J 

Purpurin is contained in madder root, and is therefore found 
in madder alizarin. It can be made by melting alizarin-sul- 
phonic acid with caustic potash, by melting tri-bromanthra- 
quinone with caustic potash, and also by oxidizing alizarin or 
quinizarin with manganese dioxide and sulphuric acid. 

It dissolves in water, forming solutions that are pure red. 
With alumina mordants it gives a beautiful scarlet red. 

Anthrapurpurin, isopurpurin, CuHsCMOHX is found in 
artificial alizarin. 



Phenanthrene, CuHio, which is isomeric with anthracene, 
is also found in the higher boiling parts of coal tar. It is 
found further in " stupp," a mixture of substances obtained 
in the distillation of mercury ores in Idria. It is formed from 
dibenzyl and from o-ditolyl by passing their vapors through 
red-hot tubes : — 



C 6 H 5 . CH 

C 6 H 5 . CH, 
C 6 H 4 . CK 

C 6 H 4 . 



C 6 H 4 . CH 
C 6 H 4 . CH 



CH ? 



When oxidized, phenanthrene is converted into diphenic acid, 
which has been shown to be a di-ortho carboxyl derivative of 

diphenyl, — 

C 6 H 4 .C0 2 H 

I 
C 6 H 4 .C0 2 H 



ALIZARIN. 403 

In this process phenanthraquinone is formed as an intermedi- 
ate product. This bears to anthracene the same relation that 
anthraquinone bears to anthraquinone. The facts mentioned 
and all other facts known in regard to phenanthrene make 
it clear that this hydrocarbon is made up as shown in the 
formula 

CH CH 
CH C/=\C CH 

CH <f >— «f >CH 
CH CH^ °CH CH 

It is a derivative of diphenyl, and is made up of three benzene 
rings. The formation of phenanthraquinone and of diphenic 
acid by oxidation of phenanthene is easily explained on this 
assumption. 



CHAPTER XXI. 
GLUCOSIDES, ALKALOIDS, ETC. -CONCLUSION. 

Under the head of the sugars, reference was made (see 
p. 185) to a class of bodies called glucosides, that occur in plants. 
These substances break down under the influence of dilute 
acids or enzymes into some variety of sugar and other com- 
pounds. Thus, salicin breaks down, according to the equation 

C 6 H 4 (OH)CH 2 (OC 6 H n 5 ) + H 2 
= C 6 H 12 6 + C 6 H 4 (OH)CH 2 OH 

Glucose. Salicylic alcohol. 

into glucose and salicylic alcohol, the alcohol corresponding 
to salicylic acid. Some of the more important glucosides are 
mentioned below. 

.^Esculin, C15H16O9 + li H2O, occurs in the bark of the 
horse-chestnut tree (JEsculus hippocastanum). It breaks down 
into glucose and aesculetin : — 

Ci 5 H ]6 9 + H 2 = C 6 H 12 6 + C 9 H 6 4 . 

^Jsculin. Glucose. iEseuletin. 

Its water solution shows blue fluorescence. 

Amygdalin, C20H27NO11 + 3 H2O, occurs particularly in 
bitter almonds ; also, in the kernels of apples, pears, peaches, 
plums, cherries, etc. With emulsin, which is an aqueous ex- 
tract of almonds, amygdalin is broken down into benzoic alde- 
hyde, hydrocyanic acid, and glucose : — 

CsoHsNOn + 2 H 2 = C 7 H 6 + CKH + 2 C 6 H 12 6 . 

Helicin, CisHieO? + I H2O, is formed by the oxidation of 
salicin (which see). It has also been made artificially by 



ALKALOIDS. 405 

mixing an alcoholic solution of acetochlorhydrose with the 
potassium compound of salicylic aldehyde : — 

C 6 H 7 C10 5 (C 2 H 3 0) 4 + C 7 H 5 2 K + 4 C 2 H 6 
= C 13 H 16 7 + KC1 + 4 C 2 H 5 . C 2 H 3 2 . 

Acetochlorhydrose is formed by heating glucose with an 
excess of acetyl chloride. 

Heiicin breaks up into glucose and salicylic aldehyde. 

Myronic acid, C10H19NS2O10, is found in the form of the 
potassium salt in black mustard seed. When treated with 
myrosin, which is contained in the aqueous extract of white 
mustard seed, potassium myronate is converted into glucose, 
allyl mustard oil, and acid potassium sulphate : — 

C 10 H 18 NS 2 O 10 K = C 6 H 12 6 + C 3 H 5 . NCS + KHS0 4 . 

Salicin, CwHisO, occurs in willow bark, and in the bark 
and leaves of poplars. Its decomposition into salicylic alcohol 
and glucose has been referred to (see preceding page). 

Saponin, C32H54O18, is found in soap root (Saponaria offici- 
nalis). Its water solution forms a lather like that formed by 
soap. 

Alkaloips. 

The alkaloids are compounds occurring- in plants, frequently 
constituting those parts of the plants which are most active 
when taken into the animal body. They arc hence sometimes 
called the active principles of the plants. Many of these sub- 
stances are used in medicine. As regards their chemical char- 
acter, they are basic in the sense that ammonia is basic; they 
contain nitrogen, ami form salts, just as ammonia iKh^s. i.e. } by 
direct addition to the aoids. 'These and other facts lead to the 
belief that the alkaloids are related to ammonia —that they 
are substituted ammonias. Recently it has been shown that 
several of the alkaloids are related to pyridine v s ^ v V- 342) and 



406 GLUCOSIDES, ALKALOIDS, ETC. 

quinoline (see p. 390). Only a few of the more important 
alkaloids need be mentioned here. 

Alkaloids of Peruvian Bark. 

Quinine, C20H24N2O2 + 3 H2O. — This valuable substance is 
obtained from the outer bark of the Cinchona varieties. When 
oxidized, it yields derivatives of pyridine. In view of the 
interest connected with quinine, the discovery of its relation 
to pyridine and quinoline has led to a large number of investi- 
gations on the derivatives of these two bases, and it is probable 
that before long it will be possible to make quinine syntheti- 
cally in the laboratory. 

The salts of quinine are formed by direct addition of the 
base to the acids. Thus, we have 



Quinine hydrochloride . C 20 H 24 ]N"2O 2 . HG1 ; 
Quinine nitrate .... CaoH^NgOa . HN0 3 ; 
Quinine sulphate . . . C2oII 24 N 2 2 . H 2 S0 4 , etc., etc. 

Cinchonine, C19H22N2O, cinchonidine, C19H22N2O, and 
other bases occur with quinine in Peruvian bark. 

Cocaine, C17H21NO4, is found in coca leaves (Erythroxylon 
coca). It melts at 98° and is levo-rotatory. Its hydrochloric 
acid salt, C 17 H 21 ]Sr04 . HC1, has recently come into prominence 
in medicine, owing to the fact that it is a powerful anaesthetic. 

Nicotine, C10H14N2, occurs in tobacco leaves in combination 
with malic acid. Potassium permanganate converts it into 
nicotinic acid, which is one of the possible pyridine-monocar- 
bonic acids. 

Atropine, C17H23NO3, is found in many varieties of Solanum 
together with hyoscyamine with which it is isomeric. It is pro- 
duced from the latter by heating the latter and by treating it 



PIPERIDINE. 407 

with caustic soda. Atropine gives tr opine and tropic acid when 
boiled with hydrochloric acid or baryta water. Tropic acid 
has been shown to be a-phenyl-hydracrylic acid, 

CH 2 (OH) - CH - C0 2 H. 

I 
C 6 H 5 

Tropine, CsHisNO, the basic constituent of atropine, has 
been prepared artificially. 

Alkaloids of Opium. 

Opium is the evaporated sap which flows from incisions in 
the capsules of the white poppy (Papaver somniferum), before 
they are ripe. The three principal alkaloids contained in 
opium are morphine, codeine, and narcotine. 

Morphine, C17H10NO3 + H2O, is a crystallizable solid which 
is difficultly soluble in water, alcohol, and ether. When de- 
composed, it yields pyridine, trimethyl-amine, and phenan- 
threne, together with other products. 

Codeine, CisI&iNOs, is a mono-methyl derivative of mor- 
phine and can be prepared from it. 

Narcotine, C-H^NOt, has been shown to contain three 
methyl groups, which arc split off, as methyl chloride, when 
the substance is heated with hydrochloric acid. It is a deriva- 
tive of tetra-hydro-isoquinoline. 

Piperine, OitHmNOs, is contained in black pepper. When 
treated with alcoholic potash, it breaks down into piperidine 
and piperic acid : — 

C jr H w NO ;! + H,0 = C,II U N -f C u H 10 O 4 . 

ril't rulino. Plpertv :n>i.l, 



408 GLUCOSIDES, ALKALOIDS, ETC. 

Piperidine, C5H11N, which, as just stated, is formed by the 
decomposition of pipeline, has been made synthetically by 
treating pyridine with nascent hydrogen : — 

C 5 H 5 N + 6H = C 5 H U K 

Pyridine. Piperidine. 

It may therefore be called hexa-hydropyridine (see p. 345). 

Strychnine, C21H22N2O2, and brucine, C23H26N2O4 + 4 H2O, 

are two alkaloids that occur in mix vomica. 



In the animal body occur a large number of complicated sub- 
stances, the study of which, at this stage, would hardly be 
profitable. Thus, there are the albumins, caseins, and fibrin : 
the coloring-matters of the blood, oxy haemoglobin, haemoglobin, 
etc. A knowledge of these substances is of great importance 
for physiology, and much progress has been made in this field. 
The study of albumin in its various forms has been carried on 
for many years. It has been shown that when the albumins 
are decomposed, certain amino acids are formed, and a careful 
study of the products of decomposition under different con- 
ditions has given some insight into their chemical character. 
Much is to be hoped for from continued investigations of these 
complicated substances. 

The study of the composition of animal substances, such 
as milk, urine, etc., and of the relations of the chemical sub- 
stances occurring in the body to the processes of life, is the 
object of physiological chemistry. Without a good knowledge 
of the general chemistry of the compounds of carbon, how- 
ever, the subjects treated of under the head of Physiological 
Chemistry cannot be understood. 



INDEX. 



A. 

Abietic acid, 350. 
Acetamino-phenol, 302. 
Acetanilide, 284. 
Acetates, 59. 
Acetenyl-benzene, 370. 
Acetic acid, 57, 129. 

aldehyde, 46. 

anhydride, 61. 
Acetochlorhydrose, 405. 
Acetone, 70. 
Aceto-nitrile, 88. 
Acetophenone, 338. 
Acetyl bromide, 61. 

chloride, 61. 

iodide, 61. 

oxide, 61. 

-urea, 216. 
Acetylene, 240. 
Acid amides, 208. 

imides, 212. 

fuchsine, 358. 
Acids, 54. 

Alcohol, 155. 

Benzene, 315. 

Dibasic. 140. 326. 

Hexabasic, 329. 

Hydroxy, 155. 

Oxy, 155. 

Tribasic, 152. 
Aconitic acid. 179, 240. 
Acrolein, 232. 
Across, L88. 

Acrylic acid, L63. 

aldehyde, 232. 

Active compounds, 126. 

principles, 406. 
Adipic acid, 142, 

Adonitc, 152, 



Aesculin, 404. 
Alanin, 206. 
Albumin, 408. 
Alcohols, 34. 

Acid, 155. 

Benzene, 309. 

Di-acid, 13(5. 

Hex-acid, 153. 

Pent-acid, 152. 

Primary, 122. 

Secondary, 121. 

Tertiary, 124. 

Tetr-acid, 152. 

Tri-acid, 147. 
Aldehyde, 46, 128. 

-alcohols, 183. 

ammonia, 48. 

Benzene, 312. 

hydrocyanide, 48. 
Aldol, 188. 

condensation, 188. 
Aldoses, L83. 
Alizarin, W0. 
Alkaloids, 405. 
Ulomucic acid, L81, 
Vlloxan, 220. 
Mlyl alcohol. 229. 

-aniline, 391 , 

isosulpho-cyanate,231. 

mustard oil, 231. 

sulphide, 230. 
Allylene, 244. 
Alpha-toluic arid. 324. 
Aluminium ethyl, 105. 
Amines, 98. 

Amino-acetic acid. 158, 
204. 

acids. 202. 

a o benzene, 290. 
-benzene, 281. 

409 



Amino-benzoic acids, 321. 

-caproic acid, 206. 

-cinnamic acids, 369. 

-cinnamic aldehyde, 
391. 

compounds, 98. 

-ethane, 98. 

-ethyl-sulphonic acid, 
207. 

-formic acid, 203. 

-hydrocinnamic acid, 
326. 

-isobutylacetic acid, 
206. 

-naphthalene, 387. 

-naphthol, 389. 

-phenols, 302. 

-propionic acids. 206. 

-succinamic acid. 211. 

-succinic acid. JOT. 

-sulphonic acids, 206. 

-toluenes, 284. 
Ammonia bases. 98. 
Amygdalin, 312, 404. 
Amy] alcohols, 126. 

valerate, L34. 
Amylene, 220. 
Angelic acid, 233. 
Anhydrogeraniol, ; 1T 
Anilides, 284. 
Aniline. 281. 

blue, 359, 

dyes, 284, 359, 

salt, 2S2. 
\nisie acid. 299, 336. 

Anisol, 299. 
Anthracene, 396. 

Vnihranilic acid. 321. 
Anthranol, 399, 

Amhrapurpurin. 102. 



410 



INDEX. 



Anthraquinone, 398. 
-sulphonic acid, 400. 

Antifebrine, 284. 

Antipyrine, 292. 

Apple essence, 134. 

Arabinoses, 183. 

Arabite, 152. 

Arachidic acid, 130. 

Archil, 307. 

Aromatic compounds, 
250. 

Arsenic-methyl com- 
pounds, 103. 

Aseptol, 302. 

Asparagine, 211. 

Aspartic acid, 207. 

Atropine, 406. 

Azelaic acid, 142. 

Azo-benzene, 290. 

Azoxy-benzene, 291. 

B. 

Barbituric acid, 219. 
Bassorin, 201. 
Behenic acid, 130. 
Benzal chloride, 277. 
Benzaldoximes, 314. 
Benzene, 250. 

-diazonium salts, 285. 

-disulphonic acid, 295. 

hexabromide, 252. 

hexachloride, 274. 

series, 250. 

-sulphonic acid, 293. 
Benzidine, 291, 376. 

dyes, 376. 
Benzine, 110. 
Benzoic acid, 315. ■ 

aldehyde, 312. 
Benzophenone, 338. 
Benzoyl-amino-acetic 
acid, 323. 

chloride, 319. 

cyanide, 319. 

-formic acid, 319. 
Benzyl alcohol, 310. 

cyanide, 325. 

ethers, 311. 

salts, 311. 
Biebrich scarlet, 388, 



Bitter-almond oil, 312. 
Biuret, 216. 
Boiling-point, 8. 
Bordeaux dyes, 389. 
Borneo camphor, 350. 
Borneol, 350. 
Brassylic acid, 142. 
Brom-benzene, 274. 

-ethane, 29. 

-methane, 27. 

-naphthalene, 385. 

-picrin, 306. 

-propionic acid, 131. 

-protocatechuic acid, 
337. 
Bromoform, 28. 
Brucine, 408. 
Butane, 20, 108, 114. 
Butanic acid, 132. 
Butene, 226. 
Butter, 151. 

Butyl alcohols, 123, 128. 
Butylene, 226. 
Butyric acid, 129, 132. 

C. 
Cacodyl, 103. 

compounds, 104. 
Caffeine, 221. 
Camphanes, 349. 
Camphor, 351. 

Artificial, 339. 

Borneo, 350. 
Cane sugar, 194. 
Cantharene, 271. 
Capric acid, 129. 
Caproic acid, 129. 
Caprylic acid, 129. 
Caramel, 195. 
Carbamic acid, 203. 
Carbamide, 214. 
Carbamines, 89. 
Carbazol, 377. 
Carbinol derivatives, 126. 
Carbohydrates, 182. 
Carbolic acid, 298. 
Carbonic acid, 156. 
Carbostyril, 369, 394. 
Carboxyl, 64. 
Oarvacrol. 304, 351 , 



Case'in, 408. 
Celluloid, 198. 
Cellulose, 197. 
Cerotic acid, 130. 
Ceryl alcohol, 128. 
Cetyl alcohol, 128. 
Chlor-acetic acids, 63. 
Chloral, 53. 

hydrate, 53. 
Chlor-benzene, 274. 

-benzoic acid, 320. 

-benzyl alcohol, 311. 

-ethane, 29. 

-formic acid, 157. 

-hydrin, 149, 

-methane, 27. 

-naphthalenes, 385. 

-picrin, 101. 

-propionic acid, 131. 
Chloroform, 28. 
Cholic acid, 207. 
Chrysamine, 377. 
Cimicic acid, 233. 
Cinchonidine, 406. 
Cinchonine, 406. 
Cinnamic acid, 367. 
Cinnamyl chloride, 367. 
Citraconic acid, 239. 

anhydride, 180. 
Citrates, 186. 
Citric acid, 179. 
Coal tar, 249. 
Cocaine, 406. 
Codeine, 407. 
Collidine, 342. 
Collodion, 198. 
Colophony, 350. 
Congo red, 377, 387. 
Conine, 345. 
Conyrine, 345. 
Coumaric acid, 369. 
Coumarin, 369. 
Cream of tartar, 176.' 
Creatine, 213. 
Creatinine, 213. 
Creosote, 303. 
Cresols, 303. 
Crotonic acid, 234. 
Crystal violet, 359. 
Cuminic aldehyde, 3J4, 





INDEX. 


411 




Cuminol, 314. 


Dihydroxy-succinic acids, 


Erythrite, 152. 




Cuminyl alcohol, 312. 


175. 


Erythritic acid, 168. 




Cyan-acetic acid, 141. 


-toluene, 367. 


Erythrol, 152. 




-amides, 212. 


Dihydro-xylene, 271. 


Erythrose, 183. 




Cyanates, 91. 


Diiodo-methane, 27. 


Esters, 66. 




Cyanic acid, 84. 


Dimethyl-acetylene, 244. 


Ethanal, 46. 




Cyanides, 81. 


-amine, 96. 


Ethandiol, 136. 




Cyanogen, 79. 


-aniline, 283. 


Ethane, 20, 24, 108. 




chlorides, 83. 


-benzene, 243. 


Ethanic acid, 57. 




Cyan-propionic acid, 145. 


-carbinol, 127. 


Ethanol, 37. 




Cyanuramide, 212. 


-ethyl-methane, 116. 


Ethanolic acid, 158. 




Cyanuric acid, 85. 


-ketone, 70. 


Ethene, 226. 




Cymene, 250, 269. 


-phosphine, 103. 


Ether, 42. 




Cymogene, 110. 


-xanthine, 220. 


Ethereal salts, 66. 




Cyste'in, 206. 


Dinitro-benzene, 280. 


Ethers, Compound, 66. 




Cystine, 206. 


-di-acetylene, 374. 


Mixed, 45. 




D. 


-naphthol, 389. 


Ethine, 241. 




-naphthol - sulphonic 


Ethyl acetate, 68. 




Dahlia, 359. 


acid, 389. 


-acetylene, 244. 




Dextrin, 201. 


Dioxindol, 373. . 


alcohol, 37, 128. 




Dextro compounds, 154. 


Dipentene, 348. 


aldehyde, 46. 




Dextrose, 184. 


Diphenic acid, 402. 


-amine, 05. 




Di-acetamide, 210. 


Diphenyl, 375. 


-ammonium nitrite, 00. 




-amino-diphenyl, 376. 


Diphenyl-amine, 283. 


-benzene, 2(54. 




Diastase, 196. 


-amine orange, 296. 


bromide, 20. 




Diazo-amino compounds, 


ether, 300. 


butyrate, 133. 




290. 


-imide, 377. 


carbamine, SO. 




-benzene compounds, 


-iodonium hydroxide, 


carbinol, r_'7. 




285. 


275. 


chlor-carbonate, 157. 




Diazonium salts, 285. 


ketone, 338. 


chlor-formate, 157. 




Di-brom-benzene, 275. 


-methane, 353. 


chloride, 20. 




Dichlor-acetic acid, 63. 


-phthalide, 360. 


cyanide, 87. 




-ethanes, 31. 


-tetrazonium chloride, 


Ethylene, 22(5. 




-isoquinoline, 395. 


387. 


alcohol, 136. 




-toluene, 277. 


Dipropargyl, 217. 


bromide. 137, 227. 




Dichlorhydrin, 149. 


Di-sodium glycol, 137. 


ohlorhydrin, 137. 




Di-cyan-diamide, 212. 


Diterpenes, 346. 


cyanide, 1 1.">. 




Di-ethylene derivatives, 


Dodecane, 108. 


-glycol, 136. 




244. 


Dulcite, L54. 


-lactic acid. 163. 




Diethyl-amine, 95. 


Durene, 250. 


-succinic acid, 115. 




-glycol other, 137. 


Dynamite, 151. 


Ethyl ether. 42. 




-phosphine, 103. 


Dyeing, 358. 


-glycol ether, 137. 




-phosphinic acid, 103. 


Dyes, 355, 370. 


-glycolic acid. 159. 




-phosphoric acid, 68. 




Ethylidene chloride. 




Dihydro-anthracene, 307. 


E. 


50, 139, 227. 




-benzenes, 271. 


Emerald green, 60. 


-lactic acid. ltd. 




Dihydroxy - anthraqnin- 


Emulsin, 404. 


-succinic acid. L46. 




one, loo. 


Enzymes, 184. 


Ethyl iodide. 29. 




-benzenes, 304. 


Eosin, 364. 


Isocyanide, 89. 




-naphthoquinone. 390. 


Eruoic aeid. 233. 


isosulphocyanate. 92. 





412 



INDEX. 



Ethyl-mercaptan, 74. 
methyl ether, 45. 
mustard oil, 93. 
nitrate, 68. 
phenyl ether, 300. 
phosphate, 68. 
phosphines, 103. 
phosphinic acid, 103. 
phosphoric acid, 68. 
sulphate, 68. 
-sulphonic acid, 75. 
-sulphuric acid, 42, 

68. 
-urea, 216. 

F. 

Fats, 151. 
Fatty acids, 129. 
Fehling's solution, 186. 
Fermentation, 38. 

Alcoholic, 38. 

Lactic acid, 38. 
Ferments, 38. 
Ferricyanides, 82. 
Ferrocyanides, 82. 
Fibrin, 408. 
Flashing-point, 110. 
Fluorescein, 363. 
Formal, 46. 
Formalin, 46. 
Formic acid, 54, 129. 

aldehyde, 46. 
Formo-nitrile, 88. 
Formula, Constitutional, 
15. 

Determination of, 12. 
Fructosazone, 191. 
Fructose, 187. 
Fruit sugar, 187. 
Fuchsine, 357. 
Fulminates, 102. 
Fulminic acid, 102. 
Fumaric acid, 236. 
Fusel oil, 39, 126. 

G. 

Galactonic acids, 170. 
Galactose, 192. 



Gallic acid, 337. 
Garlic oil, 230. 
Gasoline, 110. 
Gelatin sugar, 204. 
Geranial, 347. 
Geranic acid, 347. 
Geraniol, 347. 
Gluconic acids, 170. 
Glucosazone, 191. 
Glucose, 184. 
Glucosides, 185, 404. 
Glyceric acid, 168. 
Glycerin, 147. 
Glycerol, 147. 

esters, 151. 

nitrates, 151. 
Glycerose, 183. 
Glycine, 204. 
Glycocholic acid, 204. 
Glycocoll, 158, 204. 
Glycogen, 200. 
Glycol, 136. 
Glycolic acid, 158.' 
Glyoxylic acid, 174. 
Grape sugar, 184. 
Guaiacol, 305. 
Guanidine, 213. 
Guanine, 221. 
Gulonic acids, 170. 
Gulose, 192. 
Gums, 201. 
Gun cotton, 198. 



Haemoglobin, 408. 
Helianthin, 296. 
Helicin, 404. 
Heliotropine, 336. 
Hemiterpenes, 347. 
Hepta-naphthene, 271. 
Heptanes, 108. 
Heptene, 226. 
Heptyl alcohols, 128. 
Heptylene, 226. 
Heptoic acid, 129. 
Hexa-brom-benzene, 273. 
Hexachlor-benzene, 273. 
Hexadecane, 108. 
Hexahydro -anthracene, 
397. 



Hexahydro-benzene, 270. 

-cymene, 349. 

-pyridine, 408. 

-toluene, 271. 

-methyl-benzene, 250. 

-methylene, 270. 

-methyl-pararosani- 
line, 359. 

-naphthene, 270. 
Hexanes, 20, 108, 116. 
Hexene, 226. 
Hexoic acid, 129. 
Hexoses, 184. 
Hexyl alcohols, 128. 
Hexylene, 226. 
Hippuric acid, 323. 
Hofmann's violet, 359. 
Homology, 20, 108. 
Homophthalic acid; 395. 
Hj^dracrylic acid, 162. 
Hydrastine, 395. 
Hydrazines, 100, 292. 
Hydrazo-benzene, 291. 
Hydrazones, 190. 
Hydro-camphene, 271. 

-carbostyril, 326. 

-cinnamic acid, 326. 
Hydrocyanic acid. 80. 
Hydro-naphthoquinone, 

389. 
Hydroquinol, 306. 
Hydrosorbic acid, 233. 
Hydroxy-acetic acid, 158. 

acids, 155. 

-benzoic acids, 329. 

-cinnamic acid, 369. 

-crotonic aldehyde, 
188. 

-ethyl-sulphonic acid, 
165. 

-formic acid, 156. 

-methyl-tetrahydro- 
quinoline, 395. 

-propionic acids, 160. 

-quinoline, 394. 

-succinic acids, 171. 

-sulphonic acids, 165. 
Hyenic acid, 130. 
Hyoscyamine, 406. 
Hypogasic acid, 233. 



INDEX. 



413 



Imino compounds, 98. 
Inactive compounds, 126. 
Indican, 371. 
Indigo, 371. , 
Indigo-blue, 371. 

-white, 373. 
Indigotin, 371. 
Inversion, 195. 
Invert sugar, 195. 
Iodo-benzene, 274. 

-cyclohexane, 270. 

-ethane, 29. 

-methane, 27. 
Iodoform, 28. 
Iodoso-benzene, 274. 
Iodoxy-benzene, 275. 
Isatine, 322. 
Isethionic acid, 207. 
Isobutane, 114. 
Isobutyl alcohol, 124. 

-carbinol, 127. 
Isobutyric acid, 133. 
Isocyanates, 91. 
Isocyanides, 89. 
Isodiazo benzene, 288. 

-potassium, 289. 
Isohexane, 117. 
Isomerism, 31. 

Physical, 164. 
Isonitroso compounds, 

101. 
Iso-paraffins, 118. 
Isopentane, 11(5. 
Isophthalic acid, 328. 
[soprene, 347. 
tsopropyl alcohol, 120. 
Isopurpurin, 402. 
Isoquinoline, 395. 
[sosuccinic acid, L46. 
Isosulphocyanates, 92. 
[taoonic acid, 239. 

anhydride, L80, 239. 

K. 
Kairine, 396. 
Kerosene, L10. 
Ketone alcohols. 183. 
Ketones. 70. 338. 
Ketoses, 183. 



L. 

Lacmoid, 306. 
Lactic acids, 160. 
Lactones, 166. 
Lactose, 196. 
Laurie acid, 130. 
Laurinol, 351. 
Lead plaster, 148. 
Lepidine, 394. 
Leucine, 206. 
Levo compounds, 154. 
Levulose, 187. 
Limonene, 348. 
Linoleic acid, 246. 
Litmus, 307. 
Lutidine, 344. 
Lyddite, 302. 

M. 
Maleic acid, 236. 
Malic acid, 171. 
Malonic acid, 142, 144. 
Malonyl urea, 219. 
Malt, 196. 
Maltase, 197. 
Maltose, 196. 
Mannite, 153. 

hex-acetate, 154. 

hexa-nitrate, 153. 
Mannitol, 153. 
Mannoheptite, 154. 
Mannonic acids, 109. 
Manno-saccharic acid, 

153, 181. 
Mannosc. 192. 

Margaric acid, 130. 
Marsh gas, 20. 23, L08. 

series, 10S. 
Martins' yellow, 389. 
Mel amine, 212. 
Melissic acid. 130, 
Mellitic acid. 329. 
Melting-points, 8. 
Menthanes, 348. 
Menthenes, 271. 
Menthol. 349. 
Mercaptans, 74, 
Mercury ethyl, 105. 

fulminate, 102. 
Mesaconio acid. 239. 



Mesitylene, 250, 265. 
Mesitylenic acid, 325. 
Mesotartaric acid, 178. 
Mesoxalic acid, 174. 
Metaldehyde, 49. 
Metamerism, 31. 
Meta series, 262. 

-styrene, 366. 
Methanal, 46. 
Methane, 20, 23, 108. 
Methanic acid, 54. 
Methanol, 34. 
Methoxy-benzoic acid, 

299, 335. 
Methyl acetate, 68. 

acetylene, 244. 

alcohol, 34, 128. 

alcohol series, 128. 

aldehyde, 46. 

-amine, 95. 

bromide, 27. 

chloride, 27. 

cyanide. SO. 

-diethyl-methane, 117. 

-divinyl. 347. 

ethyl ether, 45. 

-glycocoll, 205. 

green. 359. 

iodide. 27. 

-isopropyl-benzene, 

2(59. 
-naphthalene. 390. 
orange, 296. 
-pentamethylene, 270. 
phenyl ether. 299. 
-phosphines, 103. 
-phosphinic acid, 103. 
-propanio acid. 133. 
-pyrocatechol, 305. 
-quinoline, 393. 

-sulphuric acid. 68 

-toluene, 261. 

violet. TOO. 
Metln lene iodide. 27. 

Milk sugar, 196. 
Mirbane, essence of, 280. 
Mixing syrup, 185. 

Molasses'. P.M. 

Monosaccharides, L82 
Mordants, 358. 



414 



INDEX. 



Morphine, 407. 
Moth balls, 380. 
Mucic acid, 181. 
Mustard oils, 92, 231. 
Myricyl alcohol, 128. 
Myristic acid, 130. 
Myronic acid, 405. 
My rosin, 405. 

N. 
Naphtha, 110. 
Naphthalene, 377. 
Naphthazarin, 390. 
Naphthenes, 270. 
Naphthionic acid, 377, 

387.' 
Naphthol, 387. 

orange, 388. 

-sulphonic acid, 388. 

yellow S, 389. 
Naphthoquinone, 389. 
Naphthylanrine, 387. 

-sulphonic acid, 387. 
Narcotine, 395, 407. 
Neo-paraffins, 118. 
Nicotine, 342, 406. 
Nicotinic acid, 342. 
Nitrites, 88. 
Nitro-benzene, 279. 

-benzoic acids, 320. 

-benzyl alcohol, 311. 

-cellulose, 198. 

-chloroform, 101. 

-cinnamic acids, 369. 

compounds, 100, 278. 
Nitroform, 101. 
Nitrogen, estimation of, 

11. 
Nitro-glycerin, 148, 151. 

-mannite, 153. 

-methane, 101. 

-naphthalene, 385. 

-phenyl-propiolic 
acid, 370. 
Nitroso compounds, 101. 
Nitro-toluenes, 280. 

-trichlormethane, 101. 
Nonane, 108. 
Nonoic acid, 129. 
Nonyl alcohol, 128. 



Normal paraffins, 114, 

118. 
Nux vomica, 408. 

O. 
Octane, 108. 
Octoic acid, 129. 
Octyl alcohol, 128. 
Oils, Drying, 229. 
Olefiant gas, 226. 
Olefm-terpenes, 347. 
Oleic acid, 233. 
Olein, 151, 236. 
Oleomargarin, 152. 
Opium alkaloids, 407. 
Optical activity, 126. 
Orcein, 307. 
Orcinol, 307. 
Ortho-phthalic acid, 327. 

series, 262. 
Osazone, 191. 
Osone, 191. 
Oxalates, 144. 
Oxalic acid, 142. 
Oxal-ureid, 218. 
Oxaluric acid, 218. 
Oxalyl-urea, 218. 
Oxamic acid, 211. 
Oxanthranol, 399. 
Oximes, 102. 
Oxindol, 325, 373. 
Oxy-acetic acid, 158. 

-benzoic acid, 334. 

-haemoglobin, 408. 

-propionic acids, 160. 
P. 
Palmitic acid, 130, 134. 
Palmitin, 134, 151. 
Papaverine, 395. 
Paper, 199. 
Parabanic acid, 218. 
Para-cyanogen, 80. 
Paraffin, 110. 
Paraffins, 108. 
Paraformaldehyde, 46. 
Paraldehyde, 49. 
Para-leucaniline, 355. 

-nitro-toluene, 284. 

-oxybenzoic acid, 334. 

-rosaniline, 356. 



Para series, 262. 

-toluidine, 284. 
Paris green, 60. 
Pelargonic acid, 129. 
Pent-acetyl-glucose, 186. 
Pentanes, 20, 108, 116. 
Pentene, 226. 
Pentoses, 183. 
Pentyl alcohols, 126. 
Perseite, 154. 
Petroleum, 109. 
Phenacetin, 302. 
Phenanthrene, 402. 
Phenetidine, 302. 
Phenetol, 300. 
Phenol, 296. 

-phthalein, 360. 

-sulphonic acids, 302. 

Triacid, 308. 
Phenyl acetate, 300. 

-acetic acid, 324. 

-acrylic acid, 367. 

-actelyne, 370. 

-butylene, 366, 391. 
Phenylene, 397. 
Phenyl-ethyl alcohol, 312. 

-ethylene, 365. 

-hydrazine, 292. 

hydrosulphide, 303. 

-hydroxyl-amine, 291. 
Phenyl-iodoso chloride, 
275. 

-ketone, 338. 

-mercaptan, 303. 

-methyl ketone, 338. 

-propiolic acid, 370. 

-propionic acid, 326. 

-propyl alcohol, 312. 

-propylene, 366. 

-salicylate, 333. 

-tolyl ketone, 338. 
Phloretin, 309. 
Phloridzin, 309. 
Phloroglucinol, 309. 
Phosphines, 103. 
Phosphorus compounds, 

103. 
Phthaleins, 327, 360. 
Phthalic acids, 326. 

anhydride, 327. 



INDEX. 



415 



Picoline, 342. 
Picric acid, 301. 
Pimelic acid, 142. 
Pineapple essence, 133. 
Pinene, 349. 
Piperic acid, 407. 
Piperidine, 345, 408. 
Piperine, 407. 
Piperonal, 336. 
Poirrier's orange, 389. 
Polymerism, 31. 
Polysaccharides, 182, 193. 
Polyterpenes, 346. 
Ponceaux dyes, 389. 
Primary alcohols, 122. 
Propandiolic acid, 168. 
Propane, 20, 108. 
Propanic acid, 130. 
Propanol, 120. 
Propanone, 70. 
Propantriol, 147. 
Propargyl alcohol, 244. 
Propene, 226. 
Propiolic acid, 245. 
Propionic acid, 130. 
Propyl alcohol, 120, 128. 

-meta-cresol, 304. 

-piperidine, 345. 

-pyridine, 344. 
Propylene, 226. 
Protocatechnic acid, 335. 
Prussian blue, 83. 
Prussic acid, 80. 
Pseudocumene, 250, 268. 
Purpurin, 402. 
Pyridine, 342. 

bases, 341. 
Pyrocatechol, 305. 
Pyrogallio acid, 308. 
Pyrogallol, 308. 
Pyrotartaric acid, 142, 

• 147. 
Pyroxylin, ins. 

soluble, L98. 



Quinaldine, 393. 
Quinine. 406. 
Quinizarin, 401. 
Quinoline, 326. 



Quinolinic acid, 343. 
Quinones, 339. 

R. 

Racemic acid, 176. 
Radicals, 37. 
Residues, 37. 
Resorcinol, 305. 
Resorcin-phthalein, 363. 
Rhamnite, 153. 
Rhamnose, 184. 
Rhigoline, 110. 
Rhodamine dyes, 302. 
Roccellic acid, 142. 
Rochelle salt, 176. 
Rosaniline, 284, 357. 
Rosin, 350. 
Ruberythric acid, 400. 

S. 
Saccharic acid, 181. 
Saccharobioses, 193. 
Saccharose, 194. 

oct-acetate, 196. 
Saccharotrioses, 193. 
Salicin, 405. 
Salicylic acid, 330. 

aldehyde, 332. 
Salol, 333. 
Saponification, 148. 
Saponin, 405. 
Sarco-lactic acid, lot). 
Sarcosine, ~o:>. 
Schweinfurth's green, 60. 
Sebacic arid, 1 12. 
Secondary alcohols, L21. 

SeidlitZ powders, 170. 

Seignette salt, 170. 
Sesquiterpenes, 346, 
Silicon tetrethyl, 105. 
Smokeless powder, LSI, 

108. 

Sodium chloride glucose, 

ISO. 

ethyl, lot. 
glucose, iso. 
glycol, L87. 
methyl, 68. 
Soluble blue, 369. 
cotton. 198. 



Sorbic acid, 245 
Sorbite, 154. 
Starch, 199. 
Stearic acid, 130, 134. 
Stearin, 134, 151. 
Stereo-chemistry, 165. 
Strychnine, 408. 
Stupp, 402. 
Styphnic acid, 306. 
Styrene, 365. 
Styryl alcohol, 366. 
Suberic acid, 142. 
Substantive dyes, 358. 
Substitution, 26. 
Substituted ammonias, 

94. 
Succinamide, 212. 
Succinic acid, 142, 145. 

anhydride, 140. 
Succinimide, 212. 
Sucrates, 195. 
Sugar of milk, 196. 
Sulphanilic acid, 295. 
Sulpho-benzoic acid, 320. 

-cyanic acid, 85. 

-cyanates, 85, 02. 
Sulphonic acids, 70, 202. 
Sulpho-urea, 210. 
Sulphur alcohols, 71. 

ethers, 7.~>. 
Sulphuric ethers, 42. 



Tannic acid, ;>37. 
Tannin, 337. 
Tartar emetic, i7.">. 
Tartaric acids, 17,~>. 
Tartronio acid, 171. 
Taurine, 207. 
Taurocholic acid, 207. 
Tautomerism, 309. 
Teracrj Lie acid, 238. 
Terecamphene, 350. 
Terephthalio acid, 328. 
Terpanes, ;^4S. 
Terpenes, 346. 
Tertiary alcohols, L24 

butyl alcohol, 1-M 

Tetra-brom- fluorescein, 
964. 



416 



INDEX. 



Tetra - chlor - methane, 

28. 
-ethyl-ammonium hy- 
droxide, 97. 
-ethyl - ammonium 

iodide, 97. 
-ethyl - phosphonium 
hydroxide, 103. 
Tetrahydro - benzenes, 
271. 
-isoquinoline, 395. 
-toluene, 271. 
Tetra - methyl - ethane, 
117. 
-phenyl-methane, 353. 
Tetrolic acid, 245. 
Tetroses, 183. 
Thalline, 395. 
Theine, 221. 
Theobromine, 220. 
Thiophenol, 303. 
Thiourea, 219. 
Thymol, 304. 
Tin tetrethyl, 105. 
Toluene, 250, 259. 

-sulphonic acid, 293. 
Toluic acids, 324. 
Toluidines, 284. 
Tolyl-carbinol, 312. 
Tri-acetamide, 210. 

-amino-triphenyl - car- 

binol, 356. 
-amino-triphenyl - me- 
thane, 355. 
-brom-phenol, 300. 



Tri-carballylic acid, 152. 

-chloracetic acid, 63. 

-chloraldehyde, 53. 
Trichlorhydrin, 149. 
Tri-chlor-methane, 28. 
Trihydroxy - anthraquin- 
one, 401. 

-benzene, 308. 

-cyanhydrin, 152. 

-cyan-triamide, 212. 

-ethyl-amine, 95. 
Tri-keto-hexamethylene, 

309. 
Trimesitic acid, 266. 
Trimethyl-amine, 96. 

-benzene, 265. 

-carbinol, 127. 

-ethyl-methane, 118. 

-phosphine, 103. 

-xanthine, 221. 
Trinitro-methane, 104. 

-phenol, 301. 

-resorcinol, 306. 

-triphenyl - methane, 
355. 
Trioses, 183. 
Triphenyl-carbinol, 355. 

-methane, 354. 

-methane dyes, 355. 
Tropaeolin D, 296. 
Tropaeolin OO, 296. 
Tropic acid, 407. 
Tropine, 407. 
Turnbull's blue, 83. 
Turpentine, 349. 



U. 

Unsaturated compounds, 
223. 

Uranin, 363. 

Urea, 214. 
salts, 217. ' 
Substituted, 217. 

Ureids, 217. 

Urethanes, 203. j 

Uric acid, 219. 

Uvitic acid, 265. 



Valeric acids, 129, 133. 
Valylene, 246. 
Vanillic acid, 336. 
Vanillin, 336. 
Veratric acid, 305. 
Veratrol, 305. 
Verdigris, 60. 

W. 
Wood gum, 201. 
spirits, 34. 



Xanthine, 220. 
Xanthogenic acid, 157. 
Xanthone, 332. 
Xylenes, 250, 260. 
Xylidines, 285. 
Xylite, 152. 
Xylose, 184. 



Zinc ethyl, 104. 



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